Sounds like my ex. We split just over 12 months ago, still married, his fiance is due to have their first baby in July. I was over East for christmas & took the kids to see him. I saw for myself that he is exactly the same with her (a teenager) as he was with me.
Plus he leaves voice messages on MY phone of them fighting & crap. Texts me to tell me the baby is a boy over a week ago (knows I would've liked another boy), but hasn't told the kids yet.
I'm interstate for a reason.