A good friend of mine was toying with the idea of inviting his ex to the wedding and asked me what I thought. I said, Are you kidding?! NO!
All I could think of was the jealousy, anger, regret among other emotions, that would bubble under the surface of polite words and blank expressions. I did some research online about this topic and the experts are saying that this boils down to RESPECT. The old flames have to be long extinguished without any hope of a future kindling. Also, you and your fiance MUST be on the same page about this issue. And if one of you is more reserved and quiet about the issue, don't assume that it's OKAY to move forward and send the invite.
Ultimately, it's probably WAY BETTER to keep exes off of the wedding list. Send them a postcard if you like. That's my advice. What would you do if you or your fiance wanted to invite an ex? Maybe it's an ex that you have children with...What would you do?