This feels over dramatic. If he really wanted to off himself out of whatever vague regrets he has he should've done it in prison.
7 years is a long ass time to not have accepted and gotten over something of this nature. At the very least he should've come to terms with his failure.
I also don't exactly get what his trauma is. He acts as if he feels bad about the murder revenge and the affects it had on the dudes daughter. The literal first thing he does is try to foist his suicide wishes on to her, completely ignoring how killing her dad ruined him.
His issues over his sister are squarely focused on himself and not what she went through.
How HE failed, how HE couldn't save her, how HE didn't come and get her, how HE brought shame on his family.
At no point is he really showing empathy or sorrow over what happened to HER, just that HE failed to live up to being a big brother.
There isn't remorse here. He's not concerned with his mother, the dudes daughter, or how his potential death will affect his mother.
This is what someone writes when they don't have actual experience with trauma and guilt.