me'ispe lujvo

s1 is a sister's spouse of m2 under law/custom/tradition/system/convention sp3.

Omit x4=s2=m1. Cf. speni, bunspe, tubyspe.

In notes:

be'aspe
x1 is a daughter-in-law (son's wife) of x2 according to law/custom x3.
bunspe
s1 is a brother's spouse of m2 under law/custom/tradition/system/convention sp3.