The Blue Lagoon (novel)

The story centers on two cousins, Dicky and Emmeline Lestrange, who are marooned with a galley cook on an island in the South Pacific following a shipwreck. The galley cook, Paddy Button, assumes responsibility for the children and teaches them how to survive, cautioning them to avoid the ``arita'' berries, which he calls ``the never-wake-up berries.''

Question: were the characters in blue lagoon brother and sister
Answer: no