tubyspe lujvo

t1 is the sibling-in-law of t2

t3: t1 is, or is a sibling of, s1, s1 is married to s2, t2 is, or is a sibling of, s2, t1=s1 and t2=s2 is not true. Cf. tunba speni

In notes:

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