Wait...WHAT? How again do you get to be your own grampa?

I was married to a widow, who was pretty as can be.
This widow, had a grown-up daughter,
Who had hair of red.
My father fell in love with her and soon they too were wed.
This made my dad my son-in-law,
And really changed my life.
Now my daughter was my mother,
Cause she was my father's wife.
And to complicate the matter,
Even though it brought me joy,
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, though it made me very sad.
For, if-if he were my uncle, then that also made him brother.
Of the widow's grown up daughter, who was of course, my stepmother.
Uh huh.
Father's wife then had a son who kept them on the run,
And he became my grandchild, for he was my daughter's son.
My wife is now my mother's mother, and it makes me blue.
Because although she is my wife, she's my grandmother too.
Now, if my wife is my grandmother, I am her grandchild, yeah.
And every time I think of it, heh! Nearly drives me wild.
Cause now I have become, the strangest case you ever saw,
As husband of my grandmother, I am my own grandpaw.
Oh I'm my own grandpaw.
I'm my own grandpaw.
It sounds funny I know, but it really is so,
Oh I'm my own grandpaw.
I'm my own grandpaw.
I'm my own grandpaw.
Talk about incest!
It sounds funny I know, but it really is so,
I'm my own grandpaw.

If you marry your grandmother, then you’re your own step-grandfather.

If you go back in time and have sex with your grandmother, then you’re your own biological grandfather.

did everyone already give up??

Time travel.