Seth's age?

I have talked about this in my journal about two years ago, but I thought this could be a good (and first!) discussion post.

My point of contention here is, contrary to popular beliefs, Seth is actually younger than both Forde and Kyle.

I present my argument (as written in my original post, with some editing and different comments) in a sequential-logic manner here:

Cut because Kors is being long-winded )