What's the joke about seniority in my hometown?

The new dean of the madhouse walked up to a patient and asked him why he was in the madhouse. "Doctor, it's like this." The patient said, "I married a widow and my daughter is an adult." My father married my daughter, so my wife became my father-in-law's mother-in-law, and my daughter became my stepdaughter and stepmother. My stepmother gave birth to a son, who became the grandson of my brother and my wife. I also have a son who became his grandfather's brother-in-law and his uncle's uncle. On the other hand, when the father mentioned his grandson, he said he was a brother-in-law, and the son called his sister grandma. Now I think I am my mother's father, my grandson's brother, my wife is the daughter of her son-in-law and her grandson's sister. Now I don't know if I am my grandfather, my brother's father or my son's nephew, because my son is my father's brother-in-law. Dean, that's why I'm here. I think staying here is much quieter than staying at home. "Hearing this, the dean fell to the ground, vomit a white desert.