Is it possible for someone you're no longer friends with to have a lasting impact on your psyche? (Details)?

My cousin and I have known each other since we were two. And for 18 years, I endured psychological, financial, and occasionally physical torture and being used by the guy for money and rides. This involved guilt trips, threats, coercion, lying, punching and kicking during psychotic episodes, and guilting me into forgiving all of that, only because of family. I finally just stopped talking him, and my life is way better now. But I just want to know if it's possible that I got some of my bad habits and low self-esteem from his influence. Or if it's just me.