sibling in law

Noun

Meaning

sibling in law (plural siblings in law)

Alternative form of sibling-in-law

A relative of one's generation, separated by one degree of marriage:
The sibling of one's spouse.

The spouse of one's sibling.

(uncommon) Co-sibling-in-law: A relative of one's generation, separated by two degrees of marriage:
The spouse of the sibling of one's spouse.

The sibling of the spouse of one's sibling.

Source: en.wiktionary.org

sibling-in-law