At what point? The time when that scene took place, or when Kirk took over command of the Enterprise from Pike? Mendez's wording is vague enough that it could be either. And I find it unlikely that the two are the same age, anyway. That would make Pike like 20 years old as of "The Cage", and that's obviously not true. No, I'm sticking with, during the scene in Mendez's office, Pike being the same age THEN as Kirk is NOW.