Royal Caribbean is currently offering a 60% discount on the cruise fare of the second guest in a cabin. If additional people are sharing your cabin, the 3rd and 4th guest will receive a 30% discount on their cruise fares.
The offer period is May 2-June 6, 2016, and cruises have to be booked during that time. The offer is good for sailings departing on or after June 2, 2016.
The recently renovated Royal Caribbean Liberty of the Seas sails weekly from Galveston, with regular Sunday departures for the Western Caribbean.
Cruise prices can vary by date. CruiseDirect lists fares in a table format that makes price comparison easy.