Lucius and Dyonisia Hemmingway were always the ones to constantly berate the muggle culture and their obsession with their version of magic whilst highhandedly playing into it to make their fortune. Ironically, both depended on it so that their family names had any sense of worth; both within the wizarding and muggle worlds. Neither family was known by the pure-blooded elite - much less respected - meaning there was a scramble to add meaning to the Hemmingway and Mareys names. Lucius and Dyonisia were the result of a hasty marriage, one that was aimed to be controversial given the twenty or so age gap between them, in a hope to be noticed. Of course, that didn't happen which led to the couple's eventual ways of making money in muggle London.
Rosalie Hemmingway was the youngest of six; two girls and four boys. Though the whole rough and tumble stereotype - with added magic of course - was very prominent within her childhood, Rosie was very much babied by her family. Anything she wanted she was mostly given, even if it was at an elder sibling's expense. Unfortunately for Rosie, this created a cyclical behaviour pattern amongst her and her siblings. Whenever she wanted something and got it in lieu of her siblings, their rough and tumble games became a lot more boisterous and harmful to Rosie which resulted in her running to their parents in which she'd be assured that it'd be okay; with the added promise of whatever she wanted. Though weak and defenceless at first, Rosie would grow up to defend herself aptly.
In fact, Rosie's first magical experience at the age of seven was in response to her siblings picking on her. Her eldest sibling, eighteen-year-old Engelise, had been tormenting Rosie with a slew of hexes; threatening to turn the child into a frog and whatnot. Naturally, overcome with fear, Rosie had attempted to create distance between the two, though it was largely futile due to how relentless Engelise was. The only way the tormenting stopped was due to Rosie's first experience. In a bid to protect herself, Rosie imagined something destructive in her mind, eyes closing as she willed it to happen. Little did she know that she had created a fire blast, scathing by Engelise and crashing into the garden pond. Though unintentional, the experience gave Rosie hope that one day she'd be able to break the cyclical chain and enact revenge on her siblings.
At eleven, like the rest of the Hemmingway siblings, Rosie was accepted into Hogwarts and was promptly sorted into Ravenclaw; an abnormality from the usual Slytherin. Though it seemed like she was a Ravenclaw by a landslide, Rosie was actually a hatstall with Slytherin being the other possibility. What overturned it, however, was her genuine love for knowledge at the time. Little did anyone know, much less herself, that this genuine love would turn into an obsession that would throw her closer to being a true, dark-wizard Slytherin.
Unlike her siblings, Rosie passed with a near stellar record and set of grades that set her out to be in good stead for whatever she wanted to do. She seemed to be on the right track at first; various applications to the ministry were submitted but after a few nasty rejections Rosie found herself searching for an alternate. Like many who turned, she found it down Knockturn Alley. Within the reaches of dark wizardry, Rosie found herself losing the innocent identity she once had, instead becoming an individual obsessed with the Dark Arts and everything about them. It was down this alley that she met her associates, a group of wizards and witches like her. What started out as a fairly innocent friendship became dark and impenetrable as aspirations of carrying out the most heinous large-scale crimes the UK had seen were born. Damage on Hogwarts turned to a terror on Diagon Alley until it reached it's final and current destination; the five being the most brutal serial killers that magical Great Britain have ever seen.
She's currently unemployed but a member of Vigilance, still trying to figure out how to enact the master plan she and her associates have formulated.