Don't mean to insult but searchbar. I used to think that too but it is actually in SPARTAN Armor if you look closely. Most likely they are Sam, Kelly, John, Fred, and Linda. And Thel Vadum' (Arbiter) wasn't Arbiter yet because this is a prequel. Not a sequel. If I'm right then we will see John as a teenager because Sam was 14 when he died and they were all born the same year.