-Parents, who I don't think we've ever met, other than maybe an anonymous moment in Fall of Reach.
-Other kids? Maybe even himself.
-Soldier (not sure. Maybe those ODSTs he wrecked.)
To be fair, it technically already has. If you collected all of the chapters of Sadie's Story in ODST you had to fight a NMPD officer near the end of the game. Technically there's also the crazy marine who fires at you in CE, but I won't count that.
This is the last I'll say about my opinion on this. I was HYPED because I thought this was an epic single player campaign trailer with mind blowing visuals that would tease into E3. My hopes were up, and the trailer reminded me of a Killzone 2 commercial that has been posted already. That's all.