I also once fell for the "we are separated but living together due to money/kids" line of bull crap. "I sleep on the couch!" The whole "I tried going back, for the kids, and...um...ok, yes we slept together but it was just the ONE time!" This was a long time ago but lesson learned. If this guy is not 100% all-in with you, ready to make a clean break from BM, get the divorce and CO, follow it, and have a business-only type relationship with BM - it's never going to work. ETA some relationships do start with an affair, and i think Tom Hanks and his wife started that way. So it's not that it can't work. But if the guy is a mess and dragging his feet on the divorce, nope. 

My XW tried to convince me that once we were divorced we could date and sleep together.  

I did not take her up on that offer. The last time I put eyes on her was as we were walking out of the courthouse after the final divorce hearing. I stepped off hte curb, sped up, and showed her my ass as I headed to the parking lot. She stood on the curb for a minute or two and was just stepping off to head to the parking lot as I pulled away. 

Not sure what her internal churn was at that point. She had been cheating for years, she pissed the Judge off with her snarky disrespectful crap during the final hearing.  I was not about to comfort her or give her a hug. I was blessedly done. Though she was the one who played the Divorce card.

Just because you have known him forever does not make him quality partner material.

Past behavior being the best indicator of future performance, IMHO he has DQd himself from the quality equity life partner pool.

Yes, stay away for good. Period. Dot. No until, just be done, stay done, and get on with living your best life.

You owe yourself that.  That includes not taking the cast off from BM's bed.

His baggage will never be gone. Even after he divorces, if he ever actually does divorce.  Not after a year post divorce, or even a lifetime post divorce. His baggage, will be yours if you ever make the mistake of re-engaging with him.

Take care of you.

Invest in living your best life. Which cannot possibly include this failed man, failed father, and failed partner. If he is included, it is not your best life.

IMHO of course.

He does want to be with BM, on some level, or he would finalize the divorce. It is more than just the kids. You get over this just like you get over any breakup. Cut off all contact and don't stalk him on social media. If you need to wallow in your hurt for a few days, do it. Then, get busy. Do whatever makes you happy. I would recommend taking a break from dating and concentrate on other aspects of your life. Make yourself happy without a man for awhile.

He says he doesn't want to be with BM.

His actions clearly demonstrate otherwise.

Categorize people by their actions and never be fooled by their words.

Take care of you. Get on with living well. He is not any part of living well.

Well said, Kloewent. As Rags often insists, 'The best predictor of future behaviour is past behaviour!' 

Yes, I agree with this completely. Men cannot be "held hostage" by women unless they want to be. He has some reason he doesn't want to end the marriage, and I promise it's not just about the kids. That, combined with the issues of his kids being hostile towards you will add up to years of heartache if you stick around.

And, I'll add that cheaters do not change. Yes, there are examples of those who have, but they're few and far between. My XH strung along the woman he had an affair with for 5 years. He was not faithful to her for even one moment of their relationship - she was shocked that when we divorced, he didn't miraculously become the perfect partner to her. By the time she got sick of his cheating and cut ties altogether, she was nearly 40. She wasted some of her best years on him. Now, I don't feel sorry for her because she never showed one ounce of remorse for participating in destroying my family (like you, she was convinced that I was a crazy/awful wife blah blah blah). I actually feel kind of vindicated that she ended their relationship in absolute misery when she was so confident that it would be "different" with her. 

If I were you, I would cut ties and never look back. You have a lifetime ahead of you, and you should find a partner who is capable of treating you well and comes with considerably less baggage. 

Not just a stamp.

You are done, right?  Like done, done. Zero contact, no leaving the door open fo try again some time down the road.. Not now, not years from now.  No booty calls, or accepting tearful phone calls of lament.  Zero, zip, nada.

Unless his STBX departs this mortal toil, she will always be an active factor. Even then she would be the Sainted BM/XW. His spawn, will be an even worse eternally active factor.

A viable formerly married/failed family breeder partner is so exceptionally rare as to be the proverbial Unicorn.  Make sure your Unicorn detector is highly tuned going forward.  Only engage in a relationship with the proverbial Unicorn BioParent.  There are non breeders out there. They are rare, but they do exist.

I count my lucky stars constantly at the blessings of my life with my incredible bride and the son we raised together.  Beyond some fairly manageable teen boy brain fart stuff, he was a great kid.  He is also a great man/adult.

Take care of   you.