Aileadh Armstrong is the youngest child - and only daughter - of Gareth and Caitlín Armstrong. The pair were Hogwarts sweetheart, both being Slytherins, while Gareth was the seeker for the Slytherin team while he was at Hogwarts and Caitlín was effectively head cheerleader. She was the most vocal supportive supporter of the Slytherin team. Gareth and Lin started dating in their third year and stayed together for the rest of their Hogwarts years, when Gareth proposed on their graduation day. Lin happily agreed.
Gareth went to play as seeker for Puddlemere United while Lin became a housewife. Things continued like that for around nine years when they decided they wanted a child. So they tried for about three months before Lin became pregnant. Nine months later, they had their oldest child and and only son, named James. Around six years later, the couple had another child - a daughter - named Aileadh. Aileadh was a happy accident and not even James knows that. Aileadh herself never found out. That secret was closely guarded by the parents. They didn't have anymore kids, and while Caitlín continued to care for the kids, Gareth continued to play for Puddlemere.
The Quidditch Playing didn't last long though, after a certain point Quidditch players start to expire. And after 18 years of playing for Puddlemere, Gareth reached his expiration point when he broke his arm, wrist and shoulder all at once. Puddlemere payed for his medical bills, but it wasn't like they needed to. The Armstrongs were ridicululy wealthy after 18 years of a professional quidditch career. Aileadh was two at the time, so she doesn't remember any of that. All she remembers is seeing her father far more often after that.
James left for Hogwarts at 11, thus leaving Aileadh as the "only child" Gareth and Caitlín had. Aileadh and James had been very close, at least as close as a six year gap between a girl and boy reasonably permitted. She liked playing princess, he was already feeling too cool for his sister since he was learning magic. Regardless, they kept an... understandable relationship. He bought her candy, she didn't bother him. They watched movies together, they kept their distance when they got tired of each other. In that aspect, Gareth and Caitlín were lucky.
Though there had been that common knowledge that Aileadh was magic (how could she not be?), she didn't actually experience it until she was eight. James had had his magical sign at that age, so it wasn't too surprising that Aileadh did, too. While James lit his mother's hat on fire in a rage after his father's career-shattering injury, Aileadh's first magical sign was more peaceful. Her parents had been having one of their fights, she magically made the vinyl record player begin playing her father's favorite artist - The Beatles. She successfully put a halt to their argument, though unbeknown to her, it continued as soon as she went to sleep that night.
Like her brother, she began to attend Hogwarts at the age of eleven. She was sorted into Ravenclaw, which she's been a part of ever since. She'd always been a quiet student, super shy, and often kept to herself. Those mannerisms were only reinforced after she lost her parents during Winter Break, in her third year. Her brother had been able to land a job as Puddlemere United's seeker, finally moving out of the minor league he'd played in post-school. As a celebation, the family made the most of the fact that it was also Winter Break, and took a cruise in the Atlantic. Unfortunately, the trip ended in disaster.
One night, during a major storm, the Armstrongs were out walking on the deck, which in theory should have been completely safe (at least according to James, but Aileadh had known it was a bad idea), and would have been alright had a rogue wave not tilted the ship dangerously, sending the Armstrong family over the side. James grabbed onto the side of the ship, and held on tight, pulling a muscle in the process. He was able to grab Aileadh, too, and haul them both onto the deck after the ship righted itself. Their parents, on the other hand, hadn't been so lucky. They were nowhere to be found, their bodies never recovered.
James' arm recovered while Aileadh was forced to return to Hogwarts. When it did, he finally went on to play for Puddlemere United (Aileadh is surprised he didn't lose his place in the roster) and took his sister in as her legal guardian. Aileadh isn't used to the change, she doubts she ever will be, as she still isn't over her parents' demise. Her coping mechanisms included listening to her father's old records and writing pieces for the novels he'd written and she'd found, as they'd been able to keep all of the possessions that remained back home.
Even though she lives with her brother and part of his team now, she still tends to have the urge to visit the house that's technically her brother's now, but she's not ready. She's really not.