The House of Tudor garnered its claim to the throne of England through the maternal line, which traced back to the Beauforts — an illegitimate line of children by Edward III's son John of Gaunt and his mistress, Katherine Swynford. This illegitimacy would normally render the whole line ineligible to inherit the throne, but this situation was made difficult when John of Gaunt and Katherine Swynford did indeed marry in 1396; a compromise was made, in that a papal bill declared the Beauforts legitimate (backed up by Parliament the following year) as did his legitimate son, Henry IV. However, he stipulated that the Beauforts, in exchange for legitimisation, must never inherit the throne.
The Beauforts were closely allied with Gaunt's legitimate line by his first marriage, the House of Lancaster. However, this did not make Henry of Richmond — later Henry VII — a legitimate heir, and neither did his father's ancestry. The legitimate heir was the Countess of Salisbury, but after the broken reigns of Queen Matilda in the early 12th century there was no precedent for women to be heirs to the throne (and wouldn't be until Mary I's accession in 1553.) Thus, a power vacuum was left, and the future Henry VI was left with the perfect opening.
Henry had spent much of his childhood in Brittany with his uncle, Jasper Tudor — he had been moved there after the murder of Lancastrian king Henry VI, and the death of his son Edward (presumably at the Battle of Tewkesbury) in 1471. At that point, young Henry of Richmond became the main face of the Lancastrian cause. He was no longer safe at Raglan Castle, the home of a leading Yorkist who would certainly have turned on them. The two fled to Brittany, while his mother Margaret Beaufort remained behind to advocate for the Lancastrians and form quiet alliances in the wake of Yorkist unpopularity, which came to a head in Richard III in 1483.
Margaret was able to make an agreement with Dowager Queen Elizabeth Woodville (wife of Edward IV) whose sons were presumably killed by Richard in the Tower of London to ensure his accession. Thus, a deal was made — that Elizabeth would support Henry's claim, if he would agree to marry her daughter Elizabeth of York and unite the houses — that would garner him key support he needed to triumph over Richard.
Two years after Richard III's accession, Henry and Jasper sailed to meet him in battle, where he was victorious at Bosworth on 22 August 1485 and declared himself Henry VII. To clear out people loyal to Richard, he would date his reign from 21 August, insinuating that all those who fought for Richard were guilty of treason.
Henry VII quickly moved to establish his kingship. In January 1486 he made good on his pledge, and married Elizabeth of York. This unified the houses and symbolised the end of the Wars of the Roses, shown by the heraldic emblem of the Tudor Rose — the Yorks' white rose laid over the Lancastrian red — which is, along with the Beaufort portcullis, still commonly seen today. The unification gave their children a stronger claim to the throne, of which they had seven, four of which survived infancy (Arthur, Henry, Margaret, and Mary) prior to Elizabeth of York's death in 1503.
Their first son Arthur, expected to inherit the throne, was born in September 1486. He was promised to Spanish princess Catherine of Aragon in 1489 through the Treaty of Medina del Campo. They married in 1501, but Arthur would die of sickness within months. The focus then turned to Henry's second son, also named Henry (the future Henry VIII.) Prior to this point, he had been expected to take a role in the church, but he would become king after his father's death in 1509, after which he would seek to marry his brother's widow. The negotiations would take a month before a papal dispensation was granted, and the negotiations were largely centred around the claim that Arthur and Catherine's marriage was never consummated. However, Catherine would not give Henry a son. She gave birth to many stillborn children, and their only son died after 52 days. Eventually, he feared the line would die out, and he was beginning to tire of his wife, six years his senior. He turned to his chief minister Cardinal Wolsey, hoping for an annulment — or rather, hoped that the previous papal dispensation would be rescinded. This would imply that Arthur and Catherine's marriage had indeed been consummated, rendering Catherine and Henry's marriage null and their sole surviving daughter, Mary, illegitimate. Wolsey failed to secure the annulment and thus fell from Henry's favour, though he continued to pursue it.
Henry aimed to marry Anne Boleyn, a lady-in-waiting of Catherine's with whom he had fallen in love. The English parliament enacted laws breaking ties with Rome, declaring the king Supreme Head of the Church of England, detaching the religious structure of England from the Catholic Church and the Pope. The newly appointed Archbishop of Canterbury, Thomas Cranmer, was then able to declare Henry's marriage to Catherine annulled. The former queen was swiftly removed from court, where she would spend the rest of her life under “protectorship” in various houses (essentially house arrest.)
Anne Boleyn gave birth to a daughter, Elizabeth, in 1533. Like Catherine, she would have various stillbirths. However, unlike Catherine, she was not simply divorced; in 1536 she was arrested on charges of high treason (for allegedly being unfaithful), witchcraft, and incest. Despite these charges most likely being made up, she was found guilty and executed in 1536.
He married four others — Jane Seymour, who gave Henry his only son, Edward VI, but died in 1537; Anne of Cleves, whom he swiftly divorced after discovering she looked nothing like her portrait; Catherine Howard, executed on similar grounds to Anne Boleyn; and Katherine Parr, who outlived him.
Henry died on 28 January 1547. His will reinstated his daughters by his annulled marriages to Catherine of Aragon and Anne Boleyn to the line of succession. Edward succeeded as Edward VI of England. Unfortunately, the boy king's regency was disturbed by the turbulent reigns of those trying to twist regency to their own advantage, the first being his uncle Edward Seymour, who took control and titled himself Duke of Somerset in February 1547, demonstrating complete control over Edward's council. He aimed to marry Mary, Queen of Scots to Edward, and thus impose Protestant religion on the Catholic Scotland. A bloody victory over the Scots at the battle of Pinkie Cleugh seemed to assure this, but the young queen was smuggled to France and betrothed to the Dauphin, later Francis II. Somerset was set back slightly by the lack of a Scottish marriage, but his decisive victory made him appear to be an unassailable ruler.
Under Somerset religious freedom was strongly restricted, which was not received well in southern, more traditionally Catholic portions of the country. The southern counties of Devon and Cornwall raised the Prayer Book Rebellion, forcing Somerset to send a military response and toughen the Crown's stance on Catholics. Mary, daughter of Catherine of Aragon, was a devout Catholic, and never renounced her faith, while Elizabeth, daughter of Anne Boleyn, was a moderate Protestant. John Dudley, Duke of Northumberland, removed a tyrannous Somerset from power as he had taken his nephew the king hostage. Under Northumberland, religious freedom decreased further, fuelled by a fear of a Catholic Queen as Mary was next in line.
Edward VI became ill in 1553. He wrote a statement rendering the will of his father null and void, bequeathing the throne to his cousin Lady Jane Grey, daughter of his aunt Princess Mary, as he too feared a Catholic regent and found Elizabeth too moderate to rule. Their relationship had also been strained by accusations of Elizabeth having had an affair with a married man in 1549, of which she was found not guilty. When Edward died in July, the throne passed to Lady Jane, who Northumberland married to his son Guildford for his own benefit. However, there was no appetite for this rule, and popular support for the rightful heir won out. Lady Jane was deposed after nine days and imprisoned, and Mary crowned Mary I of England.
Mary released key Catholic nobles from captivity and began to build her Privy Council. This proved difficult, however, as most members of it had been involved in attempting to put Lady Jane Grey on the throne. She would turn her attention to marriage, and seek an alliance through a marriage to Philip of Spain. Her English subjects were displeased, fearing the country would simply become a Habsburg outpost, and when she was adamant upon her plan rebellions began to break out — the most notable of which was Wyatt's Rebellion, which involved the father of Lady Jane. This rebellion was halted and as a result Lady Jane, her father, and her husband were all executed, as was the leader, Thomas Wyatt. Mary's Protestant sister Elizabeth, with whom the insurgents intended to replace Mary, was confined in the Tower of London and then put on house arrest.
Under the English common law doctrine of jure uxoris, the property and titles belonging to a woman became her husband's upon marriage. It was thus feared that should Mary marry, that man would become King of England, and English subjects did not want a Spaniard King of England who would care about Spanish affairs first and English second. There was no love to this marriage, it being pursued purely for the political gains it offered both. According to the marriage act, Philip would be titled "King of England", all official documents would be dated with both names, and Parliament would be called jointly — however, England would not be required to offer military assistance to Charles V, Philip's father, Philip could not act without the consent of Mary, and foreigners were not to be appointed to English office. A false pregnancy in 1555 culminated in Philip leaving court to command his armies.
Mary was well known for religious persecution, which got her the nickname "Bloody Mary". Under Mary, Protestant figures were imprisoned and burnt at the stake, including the former Archbishop of Canterbury, Cranmer. As part of the return to Catholicism, power was given back to Rome and the marriage of her parents was again declared valid, which ought to exclude her sister Elizabeth from succession. However, after another false pregnancy in 1557/58, she was forced to accept that Elizabeth would succeed her, and she died in November 1558, passing the throne onto her moderate Protestant sister.
It is here that the magical Tudor line begins — with Elizabeth I, known to Muggle society as the 'Virgin Queen.' The truth was that strain on magical-muggle relations was at its worst, and Elizabeth sought a solution to this as well as to the issue of Protestantism and Catholicism, and she eventually found it — in her favourite, Robert Dudley, 1st Earl of Leicester. There was, between them, a long-standing flirtation that had appeared to culminate in his wife, Amy Robsart, mysteriously being found dead at the bottom of a staircase in her home, around the same time as Elizabeth was reportedly considering marriage. No rumour his rivals tried would stick — why? Robert Dudley was himself a wizard, and Elizabeth seemed willing to find the moderate solution. Her family had magical links, through her great-great-grandmother Jacquetta of Luxembourg, mother of Elizabeth Woodville, who had been 'suspected' of witchcraft, and though it had turned out to be nothing, the queen herself had once suspected she may be magic.
Wanting a solution to these divisive problems, she married the Earl in secret and, with magic to veil the fact, carried and gave birth to a son, Owen in 1578. After he was safely removed unto magical society where he would be protected, Robert performed a fake 'cover marriage' to a courtier with whom he had been flirting, Lettice Knollys. To convince the rest of the story, and to protect herself should the Earl be exposed as a wizard, Elizabeth banished Knollys from court in an apparent fit of jealousy. Knollys was a witch, and this new distance from the queen allowed her and Dudley to raise the Tudor heir to initiate Robert and Elizabeth's plan — to separate the muggle and magical societies and crowns, and allow both to live in peace and harmony. As a legitimate child of the monarch, and a magical one (as was made apparent by a rather interesting display of fire) Owen would be eligible for this new crown, and he would spend the next twenty years trying to ensure it, for much of this time in solely magical areas where people had moved to get away from persecution and violence.
He was killed by an insurgent who despised the idea of wizards being forced into hiding, and his wife Margaret went into hiding herself, pregnant with his heir. When the societies separated officially at last in 1692 the Tudors were living more openly, the risk passed.
However, when Princess Charlotte was recognised as magical regent sometime after, the Tudors were enraged that they had their birthright seized from them. It was their belief they had a right to the throne, but to appease them and stifle mutterings of outright rebellion from the Tudor House, it was agreed that in return for fealty, members of the House of Tudor would be styled Lord / Lady of House Tudor, and the family as a whole would receive an amount of land, similar to the agreement reached upon between the new Monarchs and House Boleyn, with whom the Tudors had forged a tentative peace with, following their decision to sign an acknowledgement dismissing the false charges against Anne Boleyn. The Tudors were amenable to this settlement, and thus it has been to this day, although it would not do to raise the Tudors' ire — at the end of it all, they still have a claim to the throne.
Lady Cassandra Tudor's parents, Lord Bernard and Lady Jane Tudor, were the most progressive of their generation. Which was really quite fortunate, when you came to think about it, considering Cassie was never one to keep her mouth closed. Now, Bertrand and Jane may be very progressive, but they are also — perhaps for that reason — immensely publicly popular, and successful, bringing grand amounts of revenue into the family. Bertrand works for an international wizarding law firm, while his wife Jane has shares in a multitude of European and North American wizarding companies. If they were to be disowned, they'd take their money with them — and would likewise leave if any of their children were forced to — which is why, in spite of the fact they're not well liked by the more conservative branches of the family, they and their children remain at Tudor Castle.
It took a good deal to teach her to be quieter about her natural inherent ability — not her magic, but the fact that she was born a legilimens. Now, Cassie is the elder of twins, the other being Winnifred (who she calls Frannie) who is her junior by seven minutes, though you'd never guess it to be that little by the huge deal she makes of it, and she has another brother, TBD. The three of them are pretty tight, and Cassie would die for either one of them. She was four when she created a loud airhorn noise, almost like an "argument alarm" that kept going off whenever her uncle and grandfather went to argue with her parents. It persisted for the full day, but she still regrets that it wasn't permanent and that she never learned how to do it again.
When Cassandra turned eleven, she as all Tudors since Owen in the early eighteenth century had, received her to attend Hogwarts — where she would be sorted into TBD, and her twin sister into TBD. It was at Hogwarts that Cassie has had the most fun with her legilimency abilities — she sometimes doesn't even realise she's prying, but often she does, some people's minds are just teasingly open — and that she came to understand that she was pansexual. Cassie isn't yet open about it with her extended family, but she will have leverage that others in her family do not, secrets exposed in foolish moments with thoughts left unguarded, that she completely intends to use to keep her in the family fold if people decide to try and take the risk of her parents (and her parents' money) departing with her.