i dont think it would be selfcest!! they arent the same person, they were just created off similar blueprints.
but to answer your question... grey would find the idea of kissing pink quite disgusting! he wants to blow pink into as many little pieces as possible. unfortunately for him they have a LOT of extra lives.
when grey shows up, what usually happens is he tries to recklessly use some fancy new weapon on the pinks, and they incapacitate him with silly antics. he gets his toys taken away, gets kicked out the door, rinse and repeat. he doesn't seem to learn...!
