The ratio between the the gap in their ages and their ages is larger when they are younger. This is why age difference in a couple becomes less significant as they both grow older. Five years is a big difference between teenagers but not between octogenarians.

25/31 < 31/37. There, I did the math for you. Now if you did the downvote, would you kindly consider undoing it?

Wrong maths bro, we're talking about the ration between the difference in their ages and their ages, so 6/31 > 6/37

Nope, jstmpfile had it right.

  > 25/31 < 31/37. 

Is what I meant. Clearly I should have been more specific.