Dennis Warner’s version (use capo on 2^nd fret):

 

Intro:

   C                     C                    …                                C

½---------------   ½---------------   ½…      ----------------    ½---------------   ½

½-1-----1------  ½-1-----1------  ½…      -1-----1------     ½-1-----1------  ½

½-----0------0-  ½-----0------0-  ½…      ----------------    ½-----0------0-  ½

½---------------   ½---------------   ½…      -----0---------    ½---------------   ½

½-3------------   ½-3------------   ½…      -3-----0---2--    ½-3------------   ½

½---------------   ½---------------   ½…      -----3---------    ½---------------   ½

 

[C] Many, many years ago when [G] I was twenty-three
I was married to a widow who was [C] pretty as could be
This widow had a grown-up daughter [F] who had hair of red
My [D] father fell in love with her and [G7] soon the two were [G] wed

 

Chorus:

Now [G] I'm my own grand[C]pa, [F] I'm my own grand[D]pa[D*]
It may sound [C]funny I know, but [F]really it's so
[C] I'm my [G] own grand[C]pa

 

D*:       [x x 0 7 7 5]     this chord is optional!

 

This [C] made my dad my son-in-law and [G] changed my very life
My daughter was my mother, 'cause she [C] was my father's wife
And to complicate the matter even [F] though it brought me joy
I [D] soon became the father of a [G7] bouncing baby [G] boy

 

Now the [C] little baby then became a [G] brother-in-law to Dad
And so became my uncle though it [C] made me very sad
Cause if he was my uncle then this [F] also makes him brother
To the [D] widow's grown-up daughter who was [G7] also my step-[G]mother

 

Chorus

 

[C] Father's wife then had a son who [G] kept him on the run
He became my grandchild 'cause he [C] was my daughter's son
My wife is now my mother's mother [F] and it makes me blue
Be[D]cause although she is my wife she is [G7] my grandmother, [G]too

 

Now [C] if my wife is my grandmother then [G] I am her grandchild
And every time I think about it [C] nearly drives me wild
For now I have become the strangest [F] case you ever saw
As [D] husband of my grandmother, I [G7] am my own grand[G]pa

 

Chorus

Oh, [F] I'm my own grand[D]pa[D*]
It may sound [C]funny I know, but [F]really it's so
[C] I'm my [G] own grand, [C] I'm my [G] own grand, [C] I'm my [G] own grand[C]pa