Because I haven't played the games in a while, but I remember that Big Boss had a couple. I think it was Solidus Snake, Liquid Ocelot Revolver Ocelot, Solid Snake, Liquid Snake and Venom Snake, right? Pretty sure some of those are just me listing the same character twice, or their aliases. But then those clones made things complicated with, like, body doubles and arm- attachment hypnosis, or something? IDK. But I'm pretty sure Raiden wasn't a clone of Big Boss, right? All he was a child soldier in Africa (an oddly pale one) that the Patriots recruited, I'm pretty sure. Unless there's some intel or something I missed.
the patriots tried to mold him into a Solid Snake doppelganger, and he struggles with many of the same ethical and philosophical questions, but he's very critically his own guy.
Anyway start with MGS 1, or Metal Gear for the MSX if you're okay with old games, and play the series in release order, it's worth it.