exhusband/new girlfriend, don't respect kids' boundaries

At what point is it ok for the kids' sake to know that their father has an overnight guest, his girlfriend of 2 months? the kids just turned 4 and their father and i have been separated for 15 months, divorced for 2 months. i worry about my kids being subjected to a lot of change and i worry that they're going to be confused by it all. it just seems like he needs to wait to see if his relationship with this woman is going anywhere. i don't want my kids to be hurt.

he thinks there's nothing wrong with it and is willing to take the chance that they won't break up and that no one will get hurt.

any suggestions?

I think that you should definitely wait a few more months, before you let your kids meet his overnight guest.

They are still young, and are very fragile!