Puzzles/Action sequences/Crossing the River II

Puzzles | Action sequences | Crossing the River II

There are six persons on the shore: Three fathers and each of them has a son. The sons are afraid to be nearby a different father (or fathers) if their own father is not there (both at the boat and the either of shores). There is a boat that can hold a maximum of two persons (you can assume that the sons are able to row the boat).

How can the six people get across the river?

Solution