emlion, that sucks he came and caused trouble, but it's good Stefan was around. Someone mentioned a restraining order which you do have grounds for, and really isn't a bad idea.
I can understand your missing him. I had to cut off any communication with my brother who is much younger than I am because he's really unstable. I held him when he was a baby and cared for him when he was sick. I really loved him. But now he's dangerous and isn't really in touch with reality. And he's violent. You can keep the memories of the good times you had with him, but you need to step away because what he is is ultimately not good for you.
Maybe it seems forward of me to say this, but it seems like your relationship with him is a symptom of issues that are demanding attention from you. You must be brave and face these problems. If he stays in your life you're only putting yourself at risk and delaying having to deal with it. It will still have to be addressed. Now is your chance to cut out another aspect of the pain you've suffered in the past.
I know, unsolicited advice. I don't usually like getting it myself, so it's yours to ignore or think about. I'm only going out on a limb and giving it because I care about you.