MIL was 16, nearly 17 when I was born. So technically she's old enough to be my mother (she could legally adopt me
.....) She is also 10 years younger than my mum and very definitely a different generation.
I think this may be one of the reasons we're not close. My SIL (her daughter) is 10 years younger than me - she was a young teenager when DH and I first met, yet MIL treats us the same.
I reckon there must be others in this situation, and probably many with smaller age gaps. So I was wondering how this affects your relationship.