That would be impolite to say exactly… but the oldest would be my current age, and the oldest relative-to-me-at-the-time was seven years my elder. Although if you want to count “made out and felt her up in public while her husband was in prison” as “been with”, then the biggest relative gap was 16 years.
I had a thing for older women as a kid. Or maybe it was married women. I was a prick.