Ah, I've never seen Advent Children. I thought they were the black robed things in FF7 that said "Reunion...". One of them had a box, I think, but I thought they all were just numbers, no names.[/QUOTE]"followers of Jenova" = Kadaj and/or Loz from FFVII: Advent children. They also have the box which contained the last bits of Jenova.
Kadaj, Loz, and Yazoo aren't from the games, but are rather the essence of Sephiroth divided into three parts by the Lifestream following his death. They basically spend the movie trying to control the minds of children with Geostigma or attempting to get the last remains of Jenova so they can become whole and Sephiroth can be reborn. Loz and Yazoo aren't too important, but Kadaj is.