Joke:Black Babies

A seventy-five-year-old guy whose hair is completely white marries a twenty-two year-old girl, and she gets pregnant.
Nine months later, he walks into the maternity ward and says to the nurse, "Well, how'd I do?"

The nurse says, "She had twins"

He says, "Heh, heh, heh. Well, I guess that goes to show, that even if there's snow on the roof, there can still be fire in the furnace."

She says, "Yeah? Well, then you'd better change filters. Both of the babies are black.'