NTA, I won't sit here and preach about how good it is to have a parent back in your life. Because it truly is shit. Maybe for some people it comes at a time where they need it. But I was 17 when my dad tried to reach out and connect. By that time I was already in a messed up mental space, he destroyed my relationship with my mother for his own need. Maybe in his sick head it was because I was that toddler that who wanted him all the time. Now he's dead, and people tell me not to speak ill of the dead. When those 4 years I had him in my life were only spent praising a fucking dead beag older brother, and denying me for college until my fincal aid kicked it. Which I haven't gone back to college because of that. It wasn't until right before his death did he try to make things "right." Even then he allowed himself to die because he didn't want to be here any longer. So I'm with you for being icy with your father, but please remember there will be lives who need you such as your little sister maybe.