u/Intelligent-Power-73

American film sometime around late 70s early 80s.
Plot: Female cousin come to visit siblings.
Some things I can remember:
1 sister jerks off brother with velvet glove.
2. Siblings drug cousin to have sex with her but the cousin doesn’t drink the mix.
3. Costume party
4. Brother has sex with cousin after the party and gets pegged by the sister.
5. It’s not his sister, it’s the cousin!

I happy that’s enough to figure this one out. Not that it helps, but it was on a VHS with Smoker and 8 to 4, so that might help with the dates some.