C - My XW introduced my girls to her new BF as well. She asked me if I wanted to meet him and I declined. I told her that as their mother I trust that she will look out for our D's and only bring men into their lives that will be a positive impact. If your not ready to meet him then don't, I was not ready to meet my XW's BF and while it doesn't really bother me too much I assume if he sticks around then I will meet him at one of our daughters activities. They have been exclusively dating for several months now though and that still has not happened.
I don't think it is selfish on your part but as you know there is nothing you can do about it. I think at this point in time you do what is best for your kids and for me that means a cordial R with him whenever we meet. I don't want to make it difficult for my kids and I never ask them questions about mommy's BF. If he ever gets brought up in conversation (which is very rarely) I will just listen to what they are saying and let them know "That it sounds like fun" or "That is nice"....something like that.