At 37, I’m two years older than my wife, which has been the average age difference for my relationships in general.
But when I was 28, I dated a woman who was 21.
And when I was 27, I dated a woman who was 48.
And in an I-swear-I’m-telling-the-truth-officer moment, I dated a woman when I was 20 who I understood to be a junior at an out-of-state college. I discovered a week later she was a junior at an out-of-state high school, and was just 16 (!!). As age differences go, I consider that was the biggest.