Can someone who has read spoilers tell me why Ain/Ian is like that to him?

I haven't read the novel but from I did learn from spoilers is that he wants revenge. Michelle's family has done things (not sure what) and that's why he wants to take revenge but doing this to Michelle. But Michelle was never involved, it's his dad and older brother.

spoilers




ian was sold to michelles dad as a sex slave when he was a kid. i wont go too much into detail about that cause it made me sick to my stomach reading it but thats why he wants revenge