User blog comment:AgentGoldfish/Comic-Con Questions for Dan and Swampy/@comment-844113-20100724204018

@Ben100.aditya: They are the same age canonically, Dan said it. (Fanonically, that's different.) And like AG said before, they've done Candace's birthday, Linda's birthday, Doofenshmirtz's birthday, and Vanessa's birthday. Everyone can't be born in summer, it would look too unrealistic. And I doubt they'll reveal Ferb's crush to his siblings.