Yep! I was shocked last month while visiting my son, who is 36 years old, when I spied some silver hairs in his usually dark brown hair. Not sure he's noticed them himself, so I didn't say anything. Not sure how old I was when I first noticed some silver strands in mine.
I recently spent a few days with my kids who are in the neighborhood age wise of yours. The youngest had quite a few gray hairs. I started graying fairly early (like later 20's) at the temples, but then, my mom started graying early also. My kids are adopted so my mom's and my early graying wouldn't pertain to their experience.