"In total, the Princess fleet has six Royal Class ships and seven Grand Class ships, and the line operates just three ships that are not part of these two groups: Sun Princess, Coral Princess and Island Princess.
Sun Princess is the line's newest and biggest vessel, and the sole ship in the line's new Sphere Class of vessels. Coral Princess and Island Princess are the line's oldest and smallest vessels and part of what's called the Coral Class."
https://thepointsguy.com/guide/princess-cruises-ships-classes/
