Allison Ensor sent me the following information, which I don't think he
would mind sharing with the wider forum.  I think he may have tracked down
the culprit!  I share his skepticism...  Quoting Allison's message:

John and Kristina, I read your posts concerning the "own grandfather."
I'm not a member of the MT Forum, so I'm writing the two of you.

In Robert L. Ripley's book "Believe It or Not," there is an item like this,
signed "Mark Twain."  The heading reads: "A Philadelphian committed suicide
and left the following note."  It is of course a convoluted thing,
beginning,
"I married a widow with a grown daughter.  My father fell in love with my
step-daughter and married her...."  After all the relationships have been
laid
out, he concludes in all caps, "I AM MY OWN GRANDFATHER!" Then
comes the attribution to Twain. Ripley gives no indication as to where this
may be found in his work, and I am doubtful that it is genuine; I've
certainly
never seen it. This item of Ripley's may have appeared as far back as the
1929
original publication of the book; I can't say. "Believe It or Not" was
issued
as a Pocket Book paperback in 1941, and what I have is the 26th printing of
that, 1945.  It's on page 184.

I do remember the song "I'm My Own Grandpa."  Whether it was inspired by
reading Ripley's item would be interesting to know.

Allison Ensor
Professor of English
University of Tennessee


John Bird