How do I deal with my ex-girlfriends new guy friend?

Me and my girlfriend spilt up 1 month ago and she has met a new guy friend.She tells me that she love's me still. But we can't move back in together because we argue all the time.We have a 4 month old daughter together.I went and picked her up this morning and talked to her 2 daughters from a previous marriage.I love her daughters and they love me they want us to get back together.But the problem was he was in our bed, they didn't know that he had stayed there.My ex was sleeping in the oldest girls room with the baby.When I saw him I told the girls and hugged them and started crying.i had brought her a dozen roses I left them there.She was sleeping and didn't talk to her
she briefly woke and called me baby and wanted a hug.I turned and walked away.Both girls we're crying because I am the best thing that ever happened to her.My parents know who the guy is they told me he beat up his last wife and that he in to meth.My ex is a recovering meth addict I helped her get off it.

Your ex sounds like she has lost her mind and is going down a very dangerous path. What is she thinking having this man in her bed with small children in the house?
My opinion is that you should remain unattached from her and just try to be there for the children. If she truly still loves you then she has no business being in a relationship with this other guy. I know you are heartbroken but her behavior in unforgivable to me. Just be there for the kids and God forbid if her new guy does start abusing her just give her support as a friend, but nothing more. You sound like a very nice person who can do much better. Hope this helps!

If u want her back then keep trying... U dont want her to relapse. Call her, try to take her and the girls out for a night of fun. Try to argue less and agree more with her. Make her feel special. Hopefully its not to late.

Until your ex gets rid of the guy, you can't do anything.