Two fathers and two sons go fishing. The catch that day isn't good, so they only catch three fish. That happens to be their only supply of food, so they split it evenly, without cutting, slicing, or mauling any of the fish. How is this possible?
There are three people fishing; a grandather, father, and son. As the grandfather is the father of the father and the father is the father of the son, there are two fathers, likewise as the father is the son of the grandfather and the son is the son of the father, there are two sons.