One day 2 fathers and two sons went fishing and they caught 3 fish How is this possible?

One day 2 fathers and two sons went fishing, they each caught a fish for a total of 3 fish. How is this possible? The answer is that there where only 3 people who went fishing. The grandfather, son and grandson.

Grandfather = Father

Grandfather's son = son (to grandfather) and father (son)

Grandson = father's son

The Young boy's father equals a father and son