Used three bases by . I call them the Royal Trio because this is the line of succession in Seaquestria. If anything happened to Queen Novo, then it would go to Skystar.
 
Now, if anything happened to Skystar, then Silverstream is next in line. Ocean Flow removed herself from the line of succession, but she left it up to Silverstream if she wanted to be left in or not. She stayed in line. though she never wants to be chosen.
 
Twilight, is a bit of a confusing part. When she chose to stay in Seaquestria, her choice put her in the line for the throne. Only Novo knows it though. But it’s a mess because Twilight and Skystar are tied to take the throne at the same time.
 
It’ll come up in the story.
 
Interesting fact about Twilight’s Pearl Necklace. It is just Silverstream’s flipped around so it would fit on Twilight.