Season 1 episode 17 :
Roger surprises Blythe at her high school, wishing to spend the day together.
Roger: I've always been known as a bit of a wordsmith. Now this is a poem I wrote when I was 15 to a young lady I was going steady with, and I don't mind confessing that I was what you kids call a playa!
Season 4 episode 24 :
Blythe writes a story about her parents as teenagers.
Blythe: It's from my dad to my mom when they were both around my age.
Blythe is probably 14-16 in season 4.