I don't know what to do here. Bio-dad lives in Colorado, I live in TN with my SO and her 3 kids whom I actively co-parent with her. We reached this arrangement because bio-dad had an affair for over 2 years before she found out...then he kicked her and the kids out, ruined her financially because he lied about their finances, and manipulated her throughout the course of their divorce. She was hurt beyond measure, and he would be a dick for months, not seeing the kids, saying he was going to come for a weekend, and then not showing up. He has been without a job until the last couple of months just because he was lazy and crashing with his girlfriend and his mom.

He even almost ruined our relationship because he told her kids and her family that he was coming back home to live with them and get back together with her (before she and I moved in together in TN)...which put family pressure on her (they don't believe in divorce even after how horrible he has been). This started by him taking an interest in the kids suddenly. He started calling every evening to talk to them. He convinced their mom he was changing, becoming a Christian, and was going to get a job where they lived so he could be close to the kids. Of course, he completely backed out after he had almost ruined my relationship with her and after the kids and her family had their hopes up. The kids were devastated. This lead to the decision to move to get away from the family pressure, to be further away from him and his painful manipulation, and to develop our relationship. So we've lived together for a couple of months and I've taken on the father role, which she agreed to and I love. She is wonderful, the kids are wonderful, and we are about to be formally engaged.

She and I have reconciled what he almost did to us, by the way, so don't want to discuss that. However, after he has not shown any interest in the kids this whole time, he only called once at Christmas to talk to them, he is now interested in talking to his kids again. He has done Facetime with them the last 3 evenings. My SO, who swears that he will not come between us again and who had said she has no interest in co-parenting with him ever just told me last night that she wants to get to where the three of us co-parent.

In an ideal situation where the bio-dad would have demonstrated interest and love for his kids and allowed their mom to have her own life free from his manipulation or judgement, I would be on board with this. But there has not been a single moment over the last 13 months of our relationship where he has shown that he is anything other than the exact oposite.

I don't want to be the bad guy that keeps him away from the kids or that tells their mom that this is unacceptable...but if he hurts them again, and he will, and if he manipulates her again, which I have no doubt he is thinking it, then when it all comes to light, I'm the one who is left to pick up the pieces of everyone's broken hearts. And it puts me on the outside because I'm not their dad...no, their dad is the man that they don't know how truly vile he has been to their mom and how little regard he has had for them.

I don't feel like my relationship with her is in jeopardy. But after he has been a son of a bitch like he has, the thought repulses me like no other that he would have a say in what goes on in our home, that he could show up at a ballgame and want to hang out, that he would dare feel any pride for the kids he has abandoned over and over that I've come to love as my own.

Help...any advice is appreciated. I know how I *do* feel...just don't quite know what I *should* feel.