Redon a envoyé les spoils originaux à CCC et Aohige apparement 
So anyways, it's pretty much as everyone guessed.
20 Kings created the World Government.
19 of those kings and their royal families moved into MarieJois and continues to rule the world as the Celestial Dragons.
The Nefetari King was the only one that didn't join them.
Since 19 royal families left their kingdom to become the CD, those kingdoms were left without their kings.
Hence they chose new kings to rule. Riku Royalty is one of them.
Donquioxte royal family was one of those that left for Mariejois to become CDs.
From the original text, it does not seem like the new kings of each nation was chosen by the CDs, but rather, the people of the nations themselves.
As for how this pertains to the current situation...
Where Doflamingo stands is still rather mysterious.
The government agent who was talking with Dofla about Moria, was NOT addressing him the way you'd expect CDs would be addressed.
The agent spoke with an authoritarian tone, and not of reverence. Same goes for the VAs at the summoning.
Which means Dofla probably isn't a straight up CD, either an outcast... a mutt... or something else.
It's kinda hard to imagine the Celestial family of Donquixote would allow Dofla to use their family name if he was just a mutt though.
