Why did Solus (1st Garlean Emperor) have some of the royal family members killed?

[myahele]

I do think that some members of the family did try to kill him or each other. Killing each other makes sense.

Perhaps the "uprising" that killed Lucia and Livia's parents was actually an attempted coup by one of the family members and their followers?

Still, why would he not have left a Will of some sort to prevent something like this. Assuming what I read was true, then it seems as if Gaius as implemental in deciding who would be the new rule of Garlemald despite his outcast status, since the Succession War would not have occurred had he still been alive. Which was why I though he at least held the Emperor's Will or something