An ugly woman was walking along the street and a guy comes and asks her, "Are those two kids yours?"

"Yes," sad the lady.

"Are they twins?"

"No, no, the girl is 12 and my boy is 7. How come you think that they are twins?"

"Because I can't believe that you've been fucked twice."

Err...ok.

A good put down yes, but a joke I'm afraid it is not.