“Well, Sam, I’ll tell you how it is. You see, I married a widow, and this widow had a daughter. Then my father, being a widower, married our daughter, so you see my father is my own son-in-law.”
“Yes, I see.”
“Then again my step-daughter is my step-mother, ain’t she? Well, then, her mother is my grandmother, ain’t she? I am married to her, ain’t I? So that makes me my own grand-father, doesn’t it?”
For those looking for it, it’s "I’m My Own Grandpa, which is a cover of The Jester’s “I’m My Own Grandpaw”.
Writers Dwight Latham and Moe Jaffe were inspired by a short Mark Twain story from the 1889 collection Wit and Humor of the Age: