When to males have sex with the same person, they become Peter In Laws.
No shit? You banged her too?! That makes us Peter In Laws!
A relational distinction. If you sleep with a girl, then your buddy sleeps with her. You are his peter-in-law. The relationship is one way. You would not be his peter-in-law unless you sleep with that girl again *after* him.
Sean Penn (Madonna's ex-husband) is the peter-in-law of Guy Ritchie (and let's face facts, a bunch of other people too!)
when you and your friends have sex with the same girl.
im glad i did'nt have sex with her then i would be peter-inlaws with half the damn town
the sophisticated terminology used to describe any two male friends who have slept with one or more of the same women
leonard: you slept with betty? so did stan! You're weiner cousins
with stan? wow!
elroy: weiner cousins
? what, are you a billyhill? we're peter-in-laws you filthy savage!
Two men who have had sex with the same woman.
John and Mark have both had sex with Sally. John and Mark are peter in laws.