Not aunt seduces not niece and then her and boyfriend

I saw this scene a while back, and it's amazing, but don't have it saved anywhere, anymore, and have not been able to find it anywhere, as I can't remember actress names, or anything.

It's an older scene, I suppose it would fall in the "retro" or "vintage" genre, though not old, my guess is 70s or 80s. Maybe 60s. It starts out with a gal dressing in front of a mirror, and I think she may start to touch herself, but soon enough her aunt walks in, and they have a chat about sexuality, which leads to the two going at it. Then the younger gal's boyfriend enters (I vaguely remember them talking about him being a sailor, or something, like he had been away for a few and coming back to visit that day), and he enters to see them going at it, and joins.

I would be quite appreciative if anyone could give me names, movie title, or links to track this down. Thank you!!
 
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