Many years ago, I was married to a widow. This widow had a grown-up daughter, my father fell in love with her, and soon the two were wed. This made my dad my son-in-law, and my daughter was my mother, because she was my father's wife. To complicate the matters, I soon became the father of a bouncing baby boy. My little baby then became a brother-in-law to Dad, and so became my uncle. If he was my uncle, that also made him the brother of the widow's grown-up daughter who, of course, was my step-mother. My father's wife then had a son, and he became my grandchild, for he was my daughter's son. My wife is now my mother's mother, and because she is my wife, she's my grandmother too. Now, if my wife is my grandmother, then I am her grandchild. Now I have become the strangest case you ever saw, as the husband of my grandmother, I am my own grandpa.
— I'm My Own Grandpa
by Willie Nelson