The Six Swans is a German fairy tale collected by the Brothers Grimm as tale number 49.
A King gets lost in a forest, and an old woman helps him, on the condition that he marry her beautiful daughter. The King has a bad feeling about this but accepts anyway. He has six sons and a daughter from his first marriage, however, and fears that the children will be targeted by his new wife; so he sends them away and visits them in secret...