When two males acknowledge having been intimate with not one, not two but three different females and remain on good terms with one another, the men are now bonded by having shared the same igloo at one time or another.
Said interactions with three different females need not have occurred at the same time.
See "Eskimo Brother". Also see "It's not gay if it's in a three way" (indirectly related concept).
M1: "Yo dude, I gotta tell you, but I totally
hooked up with that chick you boned last year."
M2: "Man, it's fine, because I did it with that other chick YOU hooked up with last year."
M1: "Dude, this would totally
be fucked up except we have also both completed our eskimo hattricks by fucking Jen."
M2: "Good point."