#28223
We're not talking about the same guy who got drunk and brought 2 women back to your apartment, are we? If so, it's obvious he doesn't care about you, let alone the child you already have and the one on the way.
If you have broken up with this guy and are asking hypothetically, then that's different. First of all, he would have to show he's faithful to you, sober and not addicted to anything. In order to truly know all this, you need to take things slowly---don't move in together until you've known him for quite sometime and know that he is willing to commit long-term to you and your kids. During the time you get to know him, you don't let your kids to get attached too soon. You only allow that if you are sure he is in this for the long haul. When he comes by to visit, you watch how he interacts with the kids. All this takes time. You don't want to rush into a relationship only to see it fail after your kids got attached. Your kids come first in your life. That means their wants and needs take precedence. They don't need a parade of men coming and going in their lives. Not every man wants to become a stepfather. If you meet a man who tells you right off he doesn't want to be a stepfather, then don't get involved with him.
I strongly urge you to get counseling to find out why you're attracted to men like the above mentioned one. Also, I strongly urge you to take some parenting classes. There are classes that require to bring your children with you if you don't have a sitter for them. When my daughter was a baby, I took a few mommy and me type classes and learned a lot from them.