Final Fantasy VII: Advent Children
The Silver Haired Men (also known as The Remnants of Sephiroth) are a group of three men that were formed when Sephiroth refused to be absorbed into the lifestream at the end of Final Fantasy VII. They serve as the main antagonists in Final Fantasy VII: Advent Children as they are searching for "mother" aka Jenova.
It is unknown when exactly the Silver Haired Men came into existance, as it could have been directly after the events of Final Fantasy VII, or it could have taken time for the cells to manifest themselves in physical form. However, it is known that they have direct contact with Jenova's conscious as they're trying to make her happy.
Fragments Of The Original
The Remnants are effectively Sephiroth split into three parts. This means that each of the Remnants only shares certain characteristics and thus, they all act in different ways. They do have one thing in common though; they all have silver hair.
Kadaj inherited Sephiroth's hatred and rage, which allows him to act as the leader of the group; Loz inherited Sephiroth's physical strength and speed, but is generally lacking on the intelligence front; and Yazoo inherited Sephiroth's charisma, which often makes him seem very feminine.
We Do As Mother Commands
Throughout Advent Children, it is very clear that the Remnants are not acting on their own consciousness. Everything they do is because they have been ordered to by Jenova. Kadaj even points out his disappointment that Jenova has chosen Sephiroth to be her son instead of him, but he will do as she wises anyway.
This is also apparant when Cloud Strife is fighting with Kadaj. When he seems defeated, he asks Jenova what he should do next. This results in Sephiroth being reincarnated through the "reunion" of Jenova's Cells and Kadaj's body.
The Demise Of The Remnants
After Kadaj's transformation into Sephiroth, he is defeated by Cloud. In his final moments, after transforming back into his original form, he mistakes Aerith's voice for that of Jenova and willingly drifts away into the Lifestream.
Loz and Yazoo don't go as gracefully, as they turn themselves into suicide bombs. They plan to destroy themselves while taking Cloud with them, but their plan fails to succeed and Cloud lives, while they perish.