I'm going to throw this theory out there!!
THAT WAS MARCUS'S SON
This game will be set 18 years or so in the future and that was Marcus and Anya's son.
JD (I think I heard him get called) well the D will be for Dominic.
we'll get to see Marcus but more as a leader/advisor role and also Cole train (possible training instructor at beginning) and of course Baird.
As I say this is just my personal theory and I'll prob be wrong but hey ho!
haha