Is he paying child support?If so this should be enough and if it is not, it is up to "them" to increase it. Like it or not your fiancee has a past and your going to have to learn how to deal with it.............."all" the children need their father. If my beau blew his kids off to spend time with me, I would lose all respect for him. Sorry it's a fact of life.....Daddy makes kids....Daddy has got to take care of kids....He .D.O.E.S. Have two households.
Being friends is much better than being enemies.....Although I do agree you should get him to stand up for you in your own home......He should be the one giving out the rules but if you do occasionally(try not to be overbearing, as they are children and children can be messy and disruptive) he should be on your side completely.......Children can sense a weakness in a relationship and will play each of you against each other......Why?Because they are children. Lighten up, you can have fun with them too, even if they are not your biological children. :)