They are my friends. They are brothers by the names of Bryan and Shawn. And Soren and Rolf are the only characters that they need to train up really. Everyone else pretty much start out killers. But it's not that they use them its that they won't use anyone else except Zihark(once), Pelleas (once), and Elincia. I mean i like the Greil Mercs to but I wouldn't use them in EVERY playthrough. I always change a few of my people us a bit to make the game fun.