Jason was born to a veela mother and pure blood father, there names James & Cassandra Pierce. His father was indifferent to him, and didn't really care if he was around. His mother on the other hand loved him and would shower him with care. He especially loved his mothers cooking. His father would constantly stave at him for being half wizard and half Veela. He wasn't accepted into either worlds, but he learned to manage. Especially when visiting his fathers family, due to him being a half-blood his fathers family rejected him, and were awfully rude to him & his mother. James wouldn't even stand up for them, which really damaged the little love his son had for him.
At the age of 5 Jason went to a family gathering, but it was on his mothers side. Most of his mothers family were female, but that didn't seem to bother him. The few half veela cousins he had he was very close with. He loved them, and treated them the way everyone should be treated: with kindness. At the age of 6 Jasons parents went out to Diagon alley to get a few essential things, but they never returned. No one, was able to find out where they went or what happened, and Jason felt abandoned, as he was forced to go live with his fathers family.
The few years he spent with his fathers family were the worst of his life. They treated him as if he were less then human. His grandmother made it known that she hated him, and would never accept him as part of the family. His grandmother even went as far as putting him in closets and locking him in there for hours. By doing this it scared him, and he now has a fear of small spaces, and will not go into a small space even if his life depended on it.
When he was 11 he received a letter from Hogwarts, much to the surprise of his grandmother. Everyone assumed he was a squib, even though he had shown many times, he was able to wield magic. He wrote back that very night telling them he would be attending that year