Two Fathers and Two Sons who are Three People

Classic Puzzle
In this place there are $2$ fathers, each accompanied by their son.

So there are $2$ fathers and $2$ sons.

Yet there are only $3$ people.

Solution
This puzzle can have a solution only if one of the fathers and one of the sons is the same person.

So:
 * there is a father;
 * there is his son, who is also a father;
 * there is his son.

The $3$ people are therefore: a grandfather, a father and a son.

Variants
This problem is often seen dressed up with further details: