Mother-in-law

A person is a son-in-law or daughter-in-law to the mother-in-law.

She and the father-in-law are the parents of the spouse and in a nuclear family of his or her sisters-in-law and brothers-in-law.
They all together are the in-laws.

In comedies, the mother-in-law is shown as the bane of the husband, who is married to the mother-in-law's daughter. Mothers-in-law are often stereotyped in mother-in-law jokes.

Hit song by Ernie K-Doe in 1961, peaked at #1 on the R&B and Pop charts.

Sansevieria trifasciata is a plant commonly known as Mother-in-law's tongue.