Who is Alexander and Mary Lipton from Songs of the Humpback Whale and what is their importance?

Alex and Mary Lipton are the parents of Jane and Joley are Alexander and Mary Lipton. Alexander is an abusive alcoholic who strikes his wife and molests his daughter. He uses his charm and social standing to convince a police officer that Jane ran away because of her nightmares rather than his abuse. When Mary discovers Alexander's sexual abuse of Jane, Alexander breaks two of Mary's ribs, and the sexual abuse ends.