"Sister ship" refers to a ship that is similar or identical to another ship, often built at the same time by the same company. It can also refer to a ship that belongs to the same fleet or shares a similar design. Full definition
Along with sister ship Norwegian Dawn, the Norwegian Star is the fastest member of NCL's fleet, carrying 2,348 passengers at speeds up to 25 knots. (travelweekly.com)
It is one of four sister ships of the PONANT cruise line, selected as Conde Nast Traveler World's Best Small Cruise Ship, 2018. (georgiaaquarium.org)
This is the newest of Royal Caribbean Cruise Line's revolutionary Quantum Class fleet joining sister ships Quantum of the Seas and Anthem of the Seas. (dunhilltraveldeals.com)