glepanryborki'i lujvo

x1 and x2 both have had/are having (not necessarily simultaneously) sexual intercourse with x3, with the relevant difference(s) between x1 and x2 being x4.

The (rude) slang for this is "x1 and "x2 are Eskimo brothers (no genders assumed) with respect to common sexual partner x3". See also: "panryki'i".

In notes:

panryki'i
x1 and x2 have or had (not necessarily simultaneously) the same relationship to x3, that relationship being x4, with the relevant difference(s) between x1 and x2 being x5.