Why I Think Weiss Is a Sephiroth Copy

Silvery white hair, like Sephiroth

Former member of Soldier, like Sephiroth

Has a wing like, Sephiroth

Talks about the reunion, like Sephiroth and Sephiroth's clones; one of Sephiroth's clones said "welcome to my reunion" then became Sephiroth

Genesis refers to Weiss as "my brother"; Jenova is both Sephiroth's and Genesis' "mother". Since Sephiroth, Genesis and Angeal were part of Project Jenova.

In Final Fantasy VII: Advent Children Sephiroth said "I will never be a memory". He had a sick smile on his face.

Hojo had Jenova cells injected in him. He said that the cells started to control his mind and eat away at his soul. Sephiroth could control Cloud because Cloud has Jenova cells injected into him (until Cloud could break free by regaining his sense of self). Sephiroth was pulling Hojo's strings.

Hojo under the thrall of Jenova talking about taking a journey across the stars; Sephiroth talked about taking a journey across the universe like his "mother" with the earth as his vessel.

Sephiroth first tries to destroy the earth with meteor then tries to corrode and choke the world with the souls of the dead afflicted with geostigma; Weiss seeks to awaken Omega prematurely to corrode and awaken Omega which would corrode and choke the world.