Where did Kadaj and his gang come from? Are they the cloaked clones that appeared in the original game? Didn't Sephiroth kill them all?

What's the Geostigma exactly? From what I gathered, it's the infection of Jenova cells, but that doesn't make alot of sense. Isn't Cloud (along with Zack and Sephiroth) the only the character to have been injected with some Jenova? Or am I confusing it with Mako? More importantly, why would the kids have it?

I would also ask why full-form Kadaj ("Sephiroth") (yes, I don't think he's really Sephiroth) would actually have all of Sephiroth's memories and experiences, but I would guess that's just sloppy writing.

Also, how would Red XIII have kids? Isn't he the last of his race? Or did the staff overlook this?

Thanks in advance, guys.

Red XIII had kids? I must have missed 'em. Maybe he just crapped a few out on his own? Can't explain that one.

Or...any of your questions, as a matter of fact. I always just assumed that Kadaj n' friends were randomly thrown in as new characters. Geostigma? I took it the same way as you: an infection that's spreading among the people. Now that I think about it, it does seem like it's primarily the children who become ill.

Yeah, I got nothing. I'd be interested in knowing the answer to these as well.

cloud zack and sephiroth all have jenova cells cause of hojos tests, they have mako cause of soldier. the geostigma is jenova effecting the life stream its like a virus and the life stream tries to react to it but over compinsates and it starts to effect the inhabitants much like radiation in our case. watch the movie again and listin to vincent.

and kadaj is a shell for sepiroth much like a butter fly in larva stage and the turns into sepiroth when given more jenova cells. but yes it's really sephiroth.

but i still don't know as to where they came from

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Of the three antagonists, Kadaj is the only one with the capacity to become Sephiroth. According to Vincent Valentine, Kadaj is something of a larval form of Sephiroth, needing to only go a bit further in order to awaken as a manifestation of the fierce villain.
Kadaj feels a deep sorrow and perhaps disdain when coming to terms with the knowledge that he is nothing more than a puppet to Jenova and Sephiroth, that his "mother" has chosen Sephiroth to be her "true" son. Despite these misgivings, Kadaj ultimately is forced to relent in a particularly fierce battle with Cloud, when he completes the Reunion by merging his body with the remains of Jenova, causing his transformation into an avatar of Sephiroth.
As an avatar of Sephiroth, Kadaj is an extraordinary fighter, dealing vicious, swift and powerful blows with a lean long sword against Cloud's gigantic blade. He even seems to retain Sephiroth's memory as Sephiroth is linked inexorably to Jenova, whose cells are now a part of him.
Still, even with this boost of power, Kadaj is no match for Cloud's resolve and he is ultimately defeated.
Before reverting back to his normal body, Kadaj's Sephiroth avatar promises that he will "never be just a memory".
In death, Kadaj finds serenity in Aerith, now inexorably linked to Gaia, the mother and lifeforce of the planet (mirroring Sephiroth's link to Jenova) whom he calls "mother", a title thus far only used to refer to Jenova.