x1 is a non-binary parent of x2 [not necessarily biological].
See discussion associated with "dinti" concerning whether this meaning is restricted to "affirmatively nonbinary" or whether it is more general. Specifies "rirni" so as to be co-equal to but neither "patfu" nor "mamta". See also: "dinti", "rirni", "mamta", "patfu", "nunmu".