User blog comment:Poptropica411/Phineas plus Isabella equals Phineas and Ferb: Across the Second Dimension in Fabulous 2D?/@comment-3329115-20110213211355/@comment-3006892-20110224040826

I'm writing a fanfict where Ferb is 12 and Phineas is 11 and a half. I think that's the best estimation we've got.