Peter Griffin is a trans woman

Peter Griffin is the epitome of the dumb dad. He seems he has absolutely no clue how to be a supportive husband and dad. You just write him off as an idiot until "I Am Peter, Hear Me Roar".

Peter goes to a women's retreat and is forced to feel a woman's pain. This overwhelms him and allows him (or rather, her) to open up to her true self. When Peter comes home she completely different. She is a wonderful partner to Lois and she is a nurturing mother to her children. She is so convinced of her true gender that she believes she menstruates and lactates. Peter seems much more comfortable with being in that feminine role. Lois was not happy with it though. Lois tried to convince Peter's friend to make her back into a man. Peter saw that all of her friends and the love of her life were against her transition. The straw that broke the camel's back was Peter deciding between a sexual relationship with Lois and living as her true self. Consumed by her libido, she chooses Lois.

Now Peter has gotten more ridiculous over the years because he is acting out. If Lois can't accept a great woman then she will have to deal with an idiot as a husband.