New character [Need help.]

So. I've been thinking about making a new character. Well. I've already developed a personality, name, looks, ect. I just don't know what to do with his backstory. Could I get some ideas? '-'

What's their personallity and stuff like? Ideally, it should somewhat tie in with their backstory, soo....

Ooooh! This is like, my thing! I'll help to !

He's kind of quiet, and just likes to keep things at a mellow level..Let's just say. He's Maria's older brother. But things are kind of different about his backstory, which is included. =w='
This is what he looks like.

Maybe he experienced some form of trauma or tragedy that made him kind-of learn to hold back his emotions. Like someone or something he cared about was destroyed or harmed, so he just grew detatched? Or maybe he spent a lot of time around someone really talkative and energetic and didn't want to be like them or something? Sorry if this isn't helping much, I don't think I read Maria's backstory, lol.

Well. There was a big problem with Maria and her crazy-ass dad. Which drove the family to break apart.