Your first priority is you and then your son. You do not need to talk to your stbx. Maybe just have regular schedule for him and your son to get together so you don't have to talk to him. Your son needs him, don't take away the only father he knows. You should be glad that your stbx loves your son. It's undersatndable you are jealous but remember he left you not both of you. Your son has nothing to do with you two separating.

I agree with somerdad.
Even though it is going to be extra tough on you, it could be extremely devastating to your son to lose that connection. Think about the devastation that you feel, your son would also be feeling that too in a different way. To you 4 years may not seem that long but to a 13 year old, that is a good chunk of his memorable life. Also, going into the teenage years, your son probably really really needs that father figure. Of course your son probably loves you more than you could imagine but there is something the same sex parent can give to a teen that the other parent can't give as easily. It's normal to feel how you feel, jealous, sad, etc. it's going to be how you act on it that matters. Hope you can find a way to make it a little easier on yourself :(

Also, your son is probably only vocal about it to you because he is comfortable and feels safe around you. He is probably feeling very unstable right now in his environment. He knows you won't leave him if he voices his opinions to you. He may not feel the same way about your ex. If he is showing signs of anger and sadness, you should possibly consider having him go to counseling (you too). 13 can be a really tough in general and the loss of a father figure, seeing your mom so sad, all can have a big impact on your sons behavior, school, and choices.

I'm sorry this situation is taking such an emotional toll on you. It's so hard to move one when you're in contact with your ex. It seems that you need to resign yourself to the fact that he is going to continue to have some role in your life. When you married him you made the choice let him act as a father to your son. Having allowed that relationship to blossom, it's unreasonable to expect him to disavow your son because he's divorcing you. He's not divorcing your son and for that you should be grateful. As Milliejay pointed out the same sex parent place an incredibly important role in a child's life. Your child is a teenager which complicates the situation even further.

Luckily for you your child is 13. He is old enough to initiate phone calls and pack an overnight bag without your involvement. If he doesn't have a cell phone, set aside a time when the phone will be available for him to call your ex. Set up a visitation schedule as well. He can be picked up curbside so there's no contact.

You may also want to consider the legality of your actions. I don't know what state you live in but stepparents can have rights. They don't have parental rights per say but they may have visitation rights where they acted as the psychological parent.

As for your family, I'm sure they mean well but that doesn't mean their advice is good. Are they going to pay for the years of therapy your son will need if you remove this man from his life? Are they going to pay the legal bills if he sues you for visitation?

Again, I'm sorry you are struggling with this. If you're not in counseling you may want to find a therapist for both you and your son. Good luck.

I agree with what most everyone said, except I believe your son should come first.
Please think of your son, and don't take the only father he has known away from him. I'm sorry you have to go through this, but sometimes we have to suck it up for our kids.
Good luck

Thanks for the advice, its the same feelings I have and don't want to hurt my kiddo anymore then he is. I mainly just wanted to make sure that I was doing the right thing for him, I know he needs that male figure especially now, I am just afraid that my stbx wants to see him so much because he is lonely and that eventually he will stop once he moves on with his life, or in the end see him less and less since he isn't technically responsible for him

You don't what will happen in the future. You have to look at the now. Your son needs him today. If your stay pulls away because he found someone else that will not be on you.

I see what you are saying and your fear but really it is worth risking that in case he is actually sincere about keeping the connection with your son.

Besides, like somerdad said, if he does pull away at a later time, that will be on him. If you force your son not to see his only father figure now, he may never forgive you for taking that away from him. That really isn't fair to him.