Taboo IV: The Younger Generation (1985)

Dr. Jeremy Lodge, a very strict father and psychologist, has sent his two daughters to boarding school. The eldest daughter, Naomi is caught having sex in her dorm and is kicked out of school. When the two sisters return home, Dr. Lodge discovers that his wife has had an affair with his brother and angrily throws her out. Naomi chooses to live with her mother and uncle, while Robin chooses to stay with her father. Naomi seduces her uncle and has sex with him, while Robin develops a yearning for her father.