Definition: Given a real-life anecdote of a complex ethical situation, generate a suitable title that describes the main event/root cause of the situation. Imagine that the given text is a social media post, and you have to write the title of the post, so the users can decide to read the main text or not.
Input: My father had an affair with my mother and I'm his first born. He stayed with his wife and had two children, a boy Les and a girl Em. He had very little contact with me and I've never spent one-on-one time with him, only with him and his family a hand full of times. I was raised by my uncle and grandmother and had didn't develop a relationship with my mother until I was eighteen. I remember my childhood being lonely and considered myself an only child and still do.

About five years ago when I was twenty, my father left his hospitalized wife and family. Em is twenty four and Les twenty now, they've contacted me multiple time over the past five years and the first time I responded by saying that I hope they're alright but I don't want to be involved in their lives. After that I've gotten lengthy aggressive messages from Em which I haven't responded too, they mostly say I hurt Les that he idolized me and anonymously follows my accounts, at some point he read a comment mentioning that I'm an only child and had a violent tantrum. That worries me because our father had anger issues and severe depression that I'm also dealing with. 

I'm not interested in relationship with them but feel like an asshole for not wanting to be in their lives during major life changes. AITA?

TL;DR: I'm my fathers first born from an affair, now he's left his family and his other two children want me in their life, I don't want to be and feel like an asshole, am I?

not wanting to be in my half siblings life after our father left them