I have to echo the question. Why on earth are you getting married?
and being with someone since you were 17 or having kids with them isn’t an answer.
What you do is stop pursuing this an affair. Thats what you are doing. Pursuing an affair.
Chances are he isn’t ever going to leave his wife. But also, you can see what a liar is and how he is playing you whilst also playing the role of happily married man. You know this man is a liar, why do you want him?
You know he lies so why do you believe anything about him confiding in you? Or do you think he just lies to his wife, but you are so different and special he would never lie to you?
What’s best case scenario here for you? He leaves her? Your leave your dp? Then what? You create a blended family with this man you know to be a liar? Chances are the his kids will resent you, all the kids may resent the situation they are in. His wife isn’t going to wave you off into the sunset and your do probably won’t either.
So a lot of people’s whose lives are devastated, so you can involve your and your kids with someone who is proved to be dishonest?
It sounds like you know you shouldn’t be getting married and instead of dealing with that, you are playing silly buggars with yours kids lives, his kids lives, his wife’s life.
Its really easy to not kiss someone or sleep with them, concentrate on sorting your life out if you aren’t happy.