Summer in the Country (1980)

Luca arrives to spend a summer with his parents and sister, Fanny, at their beachside villa outside of Paris. Everything is taken care of by the two sexy maids (Brigitte Lahaie and an black actress known only as "XNK1905" in the European Girls Adult Film Database). Unknown to the master of the house, his two adolescent kids are discovering sex also with the help from the maids.
After the maids enjoy their afternoon off (insert sex scenes here), Luca goes to bed early so that he can steal some of his aunt's underwear to dress up in. Fanny takes a copy of Super Sex magazine (a bit of Italian porn product placement) from under her mattress and masturbates herself to sleep. Luca is plagued by flashbacks of near sexual encounters with his aunt as a young boy.
In the morning the maids find his black stockings & corset and decide to have some fun teaching him about sex. To be fair, they do the same for Fanny. With this experience behind him, and some practice with his sister, Luca finally manages to consummate his feelings for his aunt.
This is a genuinely erotic and beautifully shot hard core film, and also Brigitte Lahaie's final hard core role.