Polyandry - Wikipedia, the free encyclopedia
In social anthropology and sociobiology, polyandry (Greek: poly many, andros man) means a female forming a stable sexual union with more than one male.
The form of polyandry in which two (or more) brothers marry the same woman is known as fraternal polyandry, and it is believed by many anthropologists to be the most frequently encountered form.
I'm surpised no one mentioned this before.. I know it is probably very uncommon since most swingers are a couple , but I thought it was interesting!