My mother in law's boyfriend wants to stay at my house when I'm not there, but I have two young daughters and don't want him alone with them.
If you don't want him to be there, that is fine. It is your house.
I think many people like this guy could be a pedophile and I shouldn't take any chances.
I understand your concern. It is your duty to protect your daughters.
I think this guy could be a pedophile.
If you believe that this guy is a pedophile and you allow him alone with your two young daughters then that could be a very bad thing indeed. You should always look out for the safety of your kids and I'm proud of you for taking those extra steps.