spemamta lujvo

x1 is the mother of a spouse (mother-in-law) of x2, according to law/custom x3.

See also: spepa'u, mamtyspe, sperirni.

In notes:

be'aspe
x1 is a daughter-in-law/son-in-law (a spouse of a child of) of x2 according to law/custom x3.
mamspe
x1 is a step-parent via the mother of x2 due to marriage with the latter's mother according to law/custom x3, where said motherhood is not necessarily biological.
spepa'u
x1 is the father-in-law (father of a spouse) of x2 according to custom/law x3.
sperirni
x1 is the parent-/mother-/father-in-law (parent of spouse) of x2 according to custom/law x3.