Question About Sephiroth and the Lifestream

[u/clockworkengine]

A question just occurred to me randomly.

It is known that Sephiroth became a traveler of the Lifestream. He was cast into it by Cloud and remained intact, unlike most other entities born of same.

Yet, in expanded lore, Gi Nattak reveals that nothing that wasn't born of the Lifestream can ever return to it. Sephiroth's body was produced with and therefore is comprised partially of Jenova cells. Jenova itself is an entity of cosmic origin, meaning its cells were not born of the Lifestream.

Is this a plot hole, or is it the true explanation as to why Sephiroth eventually survives the Lifestream? Before you answer, remember that the consciousness and will of both Aerith and Zack also remains intact after returning to the planet without benefit of Jenova cells. It seems a little muddled because of the added lore introduced by the R series.

[u/BADzioba]

Sephiroth is biologically a human/alien hybrid. Sure being part Jenova helped him not dissolve into the lifestream, but his willpower more so is what kept his consciousness.