I don't see anyone in the discussion faulting Dawn for not wanting to be a custodial parent. But her "I don't want to share you with anyone, even your children" goes a lot further than that -- it sounds like she wants him to not have contact with his children. Even 20 year olds need the occasional phone call or email from their Dad.

If you were uncomfortable with your boyfriend's kids, what would your solution be? Not visiting at the same time as they do seems to me to be a an example of a reasonable solution; asking him to cut off contact with them does not.

(To say nothing of grandkids down the line, as Cereta mentions.)