I think I messed up my little brother's life

We we're living in a abusive home my mom was abusive and so was my father and his father which was my step dad at the time. His father wasn't that abusive it just my mom made him think the kids from her previous relationship was little devils. So to get down to it I wasn't in a great place lots of bad things were happy I was either 13 or 14 and my little half brother was 4 or 5 he couldn't talk yet and I gave him a hand job I was just curious what would happen I myself wasn't sexually active yet. I stopped when I got him hard and I felt disgusted that was the first and last time I ever did it. I grossed myself out I couldn't believe I did that and successful forgot about it until recently because I heard that my brother now 15 is in a state hospital now for molesting his younger brother and several other kids. I lost touch with my family after I was put in foster care when I was 15. My other siblings were not fortunate enough and we're left behind. I also heard my step dad gave up parental rights and my brother won't have anywhere to go. Would I be overstepping if I asked him to come live with me once he gets out?

If I'm honest, I think the complexity of your specific case is a little beyond me... I'd recommend professional advice if you feel able to seek it. My apologies for not being able to offer more. It sounds like a really difficult situation for you and your family to be dealing with.

Preteens do stuff like that just to know what it is and how it feels like. In that moment I know you were not thinking that this will have an effect on him and you. And I doubt it had on hime, because I was bullied in a school for lots of years all the time and when I was in a position after hitting the gym and martial arts to bully others I denied, so yeah...
And I am pretty sure that this act was not harmful for him, only you now. This is all normal part of groving up, it is called experimentation, and from what you have described I think that you must not punish yourself. Taken the whole context of difficult groving uo, into this post you were the victim first.

Try to get over it, it was just a play and experiment. And yeah call him to come to you, don't try to talk about this except if he will say anything, but I doubt. If this topic comes than say you are sorry now and acted then out of impuls, curiosity, hormones and experimentation which is all normal, trust me. You will be fine take care, and good luck.