I remember it as a jump-rope rhyme (1960s, southern Indiana):

[Boy Name] and [Girl Name] sittin' in a tree,
K-I-S-S-I-N-G.
First comes love, second comes marriage,
Then comes [Girl Name] with a baby carriage.
How many babies will there be?
1 . . . 2 . . . 3 . . .
(etc., until you miss a step jumping rope, which you ended up doing because you started laughing so hard in thinking about the couple in question having soooooo many babies!)