sephiroth clones

I just started playing ff7 again for the 3rd time and I'm doing quite well (Most of my materia's mastered and I just started 2nd disc!) but I realized that each time I've played it, I could never really figure out who you were really chasing.

Was it Sephiroth's will, or was it just another clone? I can't really figure it out because the game keeps referring to the fact that the suposed "Sephiroth" you're chasing has the tatoo number 1, but I've seen many people who say it's is will (this would make sense considering the fact that he can fly and disappear at will)

Also, are the black hooded figures with the tatoos the survivors of the Nibelheim incident which were gathered up to experiment on by Hojo?

If you know any answers let me know so I can stop thinking about this.

The sephiroth you chase most of the game is Sephiroth Clone #1. This is the reason for the tatoo on his hand. The guys in black hoods are other Sephiroth clones.

You're chasing Jenova throughout the first, and beginning part of the second, disc.

So the "Sephiroth" you're chasing on the 1st disc is just her will?

If that's true, then what's with the tatoo?