Board Thread:False Info and Speculative Discussion/@comment-5379216-20140705054016/@comment-29106979-20160717084055

I think Derek was actually meant to be 19 in the first season because if you can get your hands on a copy of the script at his first appearance there is a description of Derek which includes the age 19. However they could have changed that since Hoechlin doesn't really look 19 more early 20's.