They can work. Me and my husbands ex wife is actually best friends! We have family dinners together, just last night we all went to the fair, and me and her will have a few together we are always texting and always doing things with the kids. However no my ex and I hardly don’t get along and that’s because he refuses to. But yes its healthy and normal. It makes the kids so much more happier. My concern is why would your fiancée wouldn’t want to meet him when he’s still a big part of the kids life. For me as a parent if your serious and going to be around the kids then it’s respectful to introduce yourself and say hey I’m so and so and I would like to assure you that I’ll never let anything happen to your kids etc. it’s just a respectful thing to do. They don’t have to like one another. It when kids are involved it’s a nice thing. However he doesn’t have to. But if dad is still in the picture there’s always going to be sports, school functions etc and they are going to be around one another.
U can all make this work really well. Depends on how much u can be selfless. Not selfish. Definitely need the bond of marriage before u do anything else (like have a child or but a house or even live together) if u truly love each other. Get over the past and set great examples for these kids.