LOL, it is.... most of the family lead characters are Ps but not all of them. Meg is probably a J (xSFJ) and that may be some of the reason she is an outcast in the family (and the show doesn't even care enough about her to give enough info to type her well). Stewie is probably also a J, and that may be why he doesn't care much for the open craziness of the rest of the family, except for Brian. I think Stewie is ENTJ, but he could be INTJ too... it's hard to tell with how his character has developed over the seasons.
Brian is likely INTP, Lois is some sort of xSxP, Chris is ISFP, and Peter is.... well it's hard to say what he is but he is sort of a high-E pure Ne type. It's a stretch to call him ENFP or ENTP because he lacks either and any kind of judgement :laughing: (I haven't even noticed Fe or Te from him) Connection, inference, and attempting the impossible in all its crazy purity...