A family size is a 1.75 liter bottle of liqour

A level of measurement, in this case it denotes one 1.75 L bottle of hard alcohol.

You're guaranteed to find at least one of these hidden in every white, suburban pantry. Their main purpose is to sedate soccer moms and allow their underage kids to get shit housed and try to play tennis with the cat.

Part symbolism, part synecdoche - used in place of something large or over-sized.

A Wendy's Family Size Chili is when a male eats an entire family sized container of chili from Wendy's and proceeds to butt fuck a female. Some time during inter-anal activities, the male removes his member from her glutial divide and vomits the entirety of the family sized Wendy's chili onto her ass. He then proceeds to re-insert his genitalia into her vaginal canal, to completion, thus attempting to make a family.

when your average bag just isn’t enough for the damn dick eater