People injected with Jenova cells = 'Sephiroth clones'. Hojo wasn't trying to clone Sephiroth directly, but rather to reproduce the experiment's success.
[q=DaMagicSausage]now isn't their 2 sepheroths... (bad spelling i know) or prehaps a ohysycal projection of one that sepheroth is giving while he is incased in materia... i thought that one of the scientists (probibly hojo) said that the first speheroth clone was the only sucessful one, was created 5 years ago... and the real sepheroth was "killed." I think i confused myself. Anyway i had those two theorys...

1. sepheroth is making a projection of himself though the materia, or 2. the first clone that was created 5 years ago was the only one that lived... maybe he was clones at he full age of 30, so now the clone is 35...
[/q]There was no 'clone made five years ago', but that's when Hojo tried to turn Cloud into a 'clone' by inundating him with Jenova cells. As for the 'two sephiroths' argument... I agree with the idea that Cloud and co are chasing a 'psychic projection' during the game. Some people say they were actually pursuing Jenova in disguise, but that argument simply doesn't survive intense scrutiny.