'Big Brother 16' -- Frankie Grande Offends Contestant's Family With 'Rape Joke'

The family of "Big Brother 16" houseguest Victoria Rafaeli is fuming mad over a joke Frankie Grande made about 2 guys teaming up to take Victoria's virginity ... and they want apologies from him AND his sister Ariana.

During the livestream on Saturday, Grande told two male houseguests they should "double team" Victoria and "take all her virginities." He then made a bunch of extremely sexual gestures. Just watch the video.

Victoria's mother, Lizabeth, tells TMZ she definitely took Frankie's comments to be a "rape joke" and feels her daughter is now a "target for rape" because producers did nothing to stop Frankie's rant.