Good afternoon and please excuse my very late entrance.
Yes, he's the son of Garrick. Gavroche was born in the 70's, so he was in Bill's class at Hogwarts. However! Gavroche was sorted into Ravenclaw, like his father. And while he was quite bookish he only got fair marks for his house, mostly because he was fascinated by reading anything at all to do with sex. It didn't matter if it was ancient positions or materials on muggle devices, Gavroche was an expert. It wasn't something he shared with his father, or really, anyone, but certainly Gavroche had access to plenty of materials because of his father's occupation.
With the regime being DE-friendly and his father having been kidnapped and tortured, Gavroche is more interested in laying low than choosing a political affiliation. Garrick's obsessive nature with wands, and his business kept his son at a distance, and in moments of anger Gavroche knows all of this mess could have been avoided if his father wasn't the bloody wand guy.
Laying low doesn't pay the bills, and once Gavroche found out about the brothel opening he felt it was only a natural thing for him to do. Sex is his area of expertise. He knows of every kink, he's studied them all relentlessly. He has and collects every kind of device, both muggle and magical. Because of his fascination with everything involving sex, his past attempts at relationships have been somewhat bumpy and hollow, and he has come across as very alienating to someone who is interested in a partnership. But! He'll do anything, try anything, and has anything you could imagine.
I'm at wmarmington@gmail.com for questions and whatnot. And now I will go back to replying to all of the things I should have already replied to!