James Carrington was born into a rather wealthy family. His father is an influential politician, and his mother is a wizarding world-famous author and celebrity. He also has a couple of siblings, three older and two younger, so it was always a constant battle for their parents' attention. James wasn't his parents' favorite, but at least he was his grandma's, who was the person who taught him how to do music and gave him the nickname, "Blue" because of how much he loved the color and refused to wear anything that was not of the shade when he was small.
The Carringtons are pure-blooded, and so all of them received their letters for magical education before they turned eleven. Blue got his after he made the chandelier fall on the dinner table when his older sister, Elena, tore up all of his music sheet. He eventually attended Ilvermorny and was sorted into Horned Serpent. At school, Blue wasn't always the most popular kid - only getting noticed for his mad piano and violin skills. His siblings were more fond of the limelight, and he actually preferred it that way. He had a close-knit group of friends whom he shared his music to, and it got him to graduate school as a happy and content as one could be.
After graduation, he was persuaded by his father to go to magical law school, and he obliged. For like a year. He eventually dropped it because he wasn't really interested, and his dad was not happy about it, but his grandmother intervened. He decided to pursue his music and started recording all the songs he wrote from his years at Ilvermorny and as a child growing up. Some of them became instant hits, and he started making his own money. He eventually got famous enough that he was finally able to finance his own travels and decided to leave home to enrich his career and to help the less privileged.
He traveled to impoverished areas in Southeast Asia and Africa, even visited Muggle communities, to do charitable work and put up free shows and benefit concerts. His work escalated enough that he was able to create his own foundation, which he named the Matilda Carrington Charity for the Impoverished of the World, after his grandmother and went to more placed to extend his help. During his travels to far-flung areas, he was also able to write more songs, often using the sceneries as inspiration for his music. He's currently well-known, young, and successful and he couldn't be more happy about it. Plus, he knows he's making change happen in the world, one step at a time, so he's really happy about that.