I don’t know if you could consider it cheating, but I definitely think its a little rediculous! It is one thing to keep a casual friendship with an ex. Especially when there are kids involved. Even if they are grown, they will still both be attending there weddings, college graduations, etc. and if would be much better for everyone if things are civil. That’s pretty much as far as it needs to go though, his kids are well past having to call mommy to see how they did on their Spanish test. I would feel hurt if my fiance spent that much time on the phone with an ex.. like shouldn’t he be doing all of this talking with me!!! I think you should put your foot down! Even some of my best friends and I only talk a few times a month!