A few things have got me thinking recently. There's over 20 years between Moon Bunny and me, the twins are younger than some of my school friends' grandchildren! Not that I am bothered personally, nor is the rabbit, but the looks we get off some people who seem to assume we're father and daughter well! Is it possible for the big an age gap between man and wife to be too big?
It changes with age, and perception
An age gap is less "accepted" when young, becomes unimportant in middle age and then becomes an issue again when older
Says more about the perception of the individual than anything else
There are "obvious" cases where a young person suddenly becomes infatuated with a rich old partner on their last legs, occasional "abusive" relationships where there is a deliberate intention to gain financially from the partner and then leave, or gain marital status for immigration reasons
Therein lies the problem, it is these that get headlines, and the perception is then that ANY such age gap must be dodgy
Personally if a couple are happy, fills each other's needs and have a secure relationship then age is irrelevant