Honestly, this could apply to a character... or YOU, the reader.
Lots of stories do not specify exact ages, but the age-gap may still be relevant. If any of the ages below are inaccurate, feel free to let me know.
The theme is: older woman X younger male. Preferably an adult male; I tried not to include entries with children. (Emphasis on "tried".) Preferably shounen or seinen (rather than shoujo or josei) and preferably not ecchi. Can't say it's easy to find a surplus of "wholesome" (appropriate) age-gap stories.
Feel free to check out my companion stack, "Falling in Love with a Taller Girl" here