Without Sulu and Chekhov, they'd all be about the same age.
This awesome T-Shirt design was made by Blueswade for Red Bubble. Check out more of Blueswade's work.
Reddit user ThatNordicGuy made these mashups of the Classic and Reboot Star Trek Casts. Shatner/Pine, Nimoy/Quinto and Kelley/Urban.