Alright. Let's go off one by one.

Tsunami: Daughter of Queen Coral and possible future queen

Glory: Literally the center of a monarchy.

Sunny: Daughter of Queen Thorn, and so far the only other possible queen besides Onyx.

The males I had a little bit more trouble with, but if you think about it, they could be royalty.

Clay: Clay is most likely gonna marry Peril, and Peril is basically the adopted daughter of Queen Scarlet, there for sister to Queen Ruby, so if Ruby died, or Peril challenged her and Clay married Peril then Clay would be king of the SkyWings.

Starflight: Sunnyflight is still possible to happen if Sunny changes her mind or if they drift together, so Starflight is a possible Prince/King.