''lets roll play....you be my mother,ok?'' ''but honey isn't your mom dead?'' ''yes sweetie that's why I want you to lay perfectly still and close your eyes''
Mommy/child role play isn't unheard of. But daddy/daughter gets more play. When it comes to role play/age play/ whatever, both people need to be on board.
I mean the only way I can see this being okay is if he's like a baby boy submissive type and he wants you to play the dominant "mommy" kind of like girls that call their lover "daddy." If that's the case, not my cup of tea, but cool, whatever. Otherwise, if you are specifically playing his mother, like with her name and mannerisms and everything, THAT is some fucked up Oepidus shit, and I would be wary of getting between the two...