Funny. I sang this on July 1 at an Open Sing. We had a 78rpm of a woman singing it. The singer could have been Judy Canova, but I think it was Esmeralda, and the flip side was probably "Hooo-eee, Ain't Nature Grand!".... Here's how she sung it, more or less....

I'M MY OWN GRANDMA

    It sounds funny, I know,
    But it really is so,
    Oh, I'm my own grandma.

1 Now many, many years ago, when I was twenty-three,
    I was married to a widower who fell in love with me.
    My hubby had a grown-up daughter who had hair of red,
    My father fell in love with her, and soon they too were wed.

Chorus    I'm my own grandma.
    I'm my own grandma.
    It sounds funny, I know,
    But it really is so,
    Oh, I'm my own grandpa.

2 This made my dad my son-in-law and changed my very life,
    For my daughter was my mother, 'cause she was my father's wife.
    To complicate the matter, even though it brought me joy,
    I soon became the mother of a bouncing baby boy. (Chorus)

3 My little baby then became a brother-in-law to Dad,
    And so became my uncle, though it made me very sad.
    For if he was my uncle, then that also made him brother
    To my husband's grown-up daughter, who, of course, was my stepmother. (Chorus)

4   Father's wife then had a son who kept him on the run,
    And he became my grandchild, for he was my daughter's son.
    My hubby is my mother's father, and it makes me blue,
    'Cause, though he is my husband he is my grandfather, too. (Chorus)

5   Now if my husband's my grandfather, then I'm his grandchild,
    And every time I think of it, it nearly drives me wild,
    For now I have become the strangest case you ever saw
    I'm married to my grandfather, so I'm my own grandma! (Chorus)

    Oh, I'm my own grandma.
    I'm my own grandma.
    It sounds funny, I know, but it really is so,
    Oh, I'm my own grandma.