They have been the butt of gags for decades, and now long-suffering mothers-in-law have had their cause taken up by the Pope, who referred to their plight during his weekly audience at the Vatican yesterday.
Conceding that mothers-in-law are "mythical figures" who are often portrayed in a poor light, the Pope appealed to Roman Catholic husbands and wives to go easy on them.
They might be "a bit peculiar" but they should not be demonised or made fun of, he said.
"The mother-in-law is a mythical figure, I'm not saying we think of her as the Devil, but we always think of her as an unpleasant figure," he told thousands of people gathered in St Peter's Square.
"But the mother-in-law is the mother of your husband or the mother of your wife. We have to get over thinking that the farther away the mother-in-law is, the better.
"Sometimes they're a bit peculiar, but they gave birth to your spouse."
He said mothers-in-law are not perfect and should guard against being too protective of their offspring once they are married.
"To you, mothers-in-law, I say be careful with your tongue because its misuse is one of the worst sins of mothers-in-law."
The 85-year-old has no personal experience of a mother-in-law as he has never married - but it is not the first time he has waded into territory that for generations provided such rich material for stand-up comics.
![Pope Francis has no personal experience of a mother-in-law as he has never married. Photo / AP](https://www.nzherald.co.nz/resizer/v2/AIVYVS3DMLHZDARLFSKNALCXRU.jpg?auth=bce42e6224cd362cc1f5b8d9474cf59882085159e39756d3e8193feb8fc7008d&width=16&height=11&quality=70&smart=true)
During a visit to the United States in 2015, he told a crowd in Philadelphia: "Families quarrel. Sometimes plates can fly. Children give headaches. I won't speak about mothers-in-law."
The remark prompted applause and laughter.
The year before, during a Valentine's Day gathering of thousands of couples in St Peter's Square, he remarked that "the perfect family" does not exist.
"The perfect husband does not exist and the perfect wife does not exist."
Then, after a pause for comic effect, he added: "Let's not even talk about perfect mothers-in-law."
The pontiff apologised for staying seated during his weekly audience, blaming a torn ligament in his knee that has forced him to cancel several engagements in recent days.