I would be out the door so fast as far as the relationship goes. He may be a great father and you will have to work out something for the children that keeps you both actively parenting, but he should have made himself single and available before experimenting with other people. So what if he's bi or gay? So what if he's found out he doesn't want a long term relationship with this guy? Does that mean he gets to keep his foot in the door of his long term relationship with you? Does that mean it's fair to keep you on the back burner while he works out who he is and what he wants? There is absolutely nothing wrong with whatever sexuality anyone has, as long as you are being respectful and not hurting anyone, but it seems like he is doing all of this at yours and your young family's emotional risk and selfishly trying to keep all of his options open. At nearly 30 he should be more sensible as regards his behaviour. I would be angry and hurt but maybe you can find a way to be understanding with him about the struggles he may be facing but to also have that firmness in your self respect that lets you say that you expect a higher level of loyalty and honesty from a partner, and that you'll have to find that it with someone else, whilst remaining friends for the children and getting together for days out and christmases and such. (I'm 25, my husband's 27, we have a nearly 7 year old daughter).