Meanings
plural co-in-laws
- rareA distant in-law: A relationship by marriage with a separation by three degrees (two people), compared to prototypical in-laws, where the separation is two/one. The separation may be two degrees of blood kin and one of marriage (addressing the mother of the husband of one's daughter), or one degree blood and two of marriage (addressing the brother-in-law of one's brother, or, similarly, addressing the wife of the brother of one's husband).
My co-in-law and I took our granddaughter to the zoo. [= co-parent-in-law]
1 more example
the co-in-law, or aŋayunġuq-nukaunġuq relationship, which involved people who married siblings [= co-sibling-in-law]
2006, Ernest S. Burch, Jr., Social Life in Northwest Alaska: The Structure of Iñupiaq Eskimo Nations, page 94Synonyms: co-affine
Synonyms & antonyms
nounA distant in-law: A relationship by marriage with a separation by three degrees (two people), compared to prototypical in-laws, where the separation is two/one. The separation may be two degrees of blood kin and one of marriage (addressing the mother of the husband of one's daughter), or one degree blood and two of marriage (addressing the brother-in-law of one's brother, or, similarly, addressing the wife of the brother of one's husband).
Origin
* co- + -in-law The usage comes from the reciprocal relationship of the two people separating the people in question, such as two men who are each father-in-law to one of the parents of their grandchildren.
Full word history & related roots →Cite this entry
co-in-law. (n.d.). In WatkinsX Dictionary. Retrieved November 4, 2026, from https://dictionary.watkinsx.com/word/co-in-law
“co-in-law.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/co-in-law. Accessed November 4, 2026.
WatkinsX Dictionary, s.v. “co-in-law,” accessed November 4, 2026, https://dictionary.watkinsx.com/word/co-in-law.
Source: co-in-law on Wiktionary, CC BY-SA 4.0.