Someone should write a ballad about the Inlaws of Sherwood Forest...

Bold Robin lay hid in the green green wood,
A man in mortal fear,
"I fear no man on earth" said he
"But my mother-in-law is near..."

But the truth is, the idea that mothers-in-law and sons-in-law are bound to be enemies is absolute nonsense. Mine almost always used to take my side in any marital discord, and I think that's pretty typical.