User blog comment:Observer Supreme/The Gorosei's Role/@comment-68.225.211.221-20161214010426

Each of them were probably important in five of the twenty kingdoms, like Admirals for their nation, and likely served as Ministers of Defense, Finance, Justice, etc, when the WG was formed. And after whatever made them immortal happened, the Kings likely made them regents and advisors for their children, and then from there, became the full rulers after the Tenryubito descended into hendoinsim and sloth.