Taboo 2 (1982)

Barbara, still luscious, is now living with the voluptuous Gina. She lusts for absent son Paul until a chance meeting with his friend, Junior McBride. Then throbbing with desire, she succumbs to the boy who reminds her of her own son. Barbara and Gina's massage session turns into frantic bi-sexual/lesbian sex and is later interrupted then wildly escalating to a threesome with visiting Junior, who had been given Barbara's address during a shopping trip earlier that day, that he learns that Barbara had been earlier having sex with her own son, Paul, his friend. From there, Junior seduces his mother, Joyce and his luscious sister, Sherry. After this chain of sexual dominoes, crowned by an orgy including a wet and dripping daisy-chain of unbridled lust, Sherry seduces her own father, Greg.