This song was written to reinforce fact families. I refer to the addition problems as the brother and sister, and the subtraction problems as the mother and father.
"Everybody say hi to the brother,
Two numbers to add,
Everybody say hi to the sister,
Switch the ones you had,
If you know the brother, look behind your back,
Because the sister is the turn-around-fact!
Add two numbers, what do you get?
Switch those numbers, it's the same I bet!"
This is a parody of "We are Family" by Sister Sledge. I am not profiting from this song and it is free for educational use.
Thumbnail from Malchows Dog Blog.