-in-law
- (to indicate that the person in question is not a direct relative but is related through marriage)
Wiktionary
suffix
Etymology: Back-formation from mother-in-law, father-in-law, brother-in-law, etc.
- Related through marriage.
“cousin-in-law”
Etymology: Back-formation from mother-in-law, father-in-law, brother-in-law, etc.
“cousin-in-law”