User blog comment:PlantyThePottedPlant/Random Topic Blogging III: Blog Harder/@comment-3006892-20130512072002/@comment-1647442-20130513044005

Phineas and Ferb are, confirmed, the same age. Original pitch states Phineas at nine, and, considering his birthday Clip-O-Rama, I'd say he and Ferb are currently ten. Ferb's birthday is likely earlier in the year. Perhaps February or something. Or, rather, Ferbuary. Candace is fifteen, Jeremy sixteen, Doofenshmirtz 47. Perry, considering how young he appears to be when they first got him five years prior to The Summer, is either five or six, but is older mentally. Think dog years, but, like, platypus years.