Two fathers and two sons went duck hunting Each shot a duck but they shot only three ducks in all How come?

The answer is four - 4

no 3, the grandfather is the father of the father. the father is the father of the son. the father is the son of the grandfather. the son is the son if the father.

Ummm . . .

Don't two fathers constitute both two fathers and two sons? We got two dead rabbits here!