Carnival requires that all passengers in a cabin are 21 or older or that at least one person in the cabin is 25 or older. An exception may be made for underage married couples, as long as they are both 18.

Yes, but they must follow strict stateroom assignment rules. Carnival Cruise Line requires that for every stateroom, there must be at least one person who is 21 years of age or older on the day of embarkation. Because one traveler is 21, the 20-year-old is permitted to sail. However, if the 21-year-old is not a relative (parent, grandparent, sibling, etc.) or legal guardian of the 20-year-old, Carnival technically requires the minor (under 21) to be in a "cross-referenced" cabin with a relative or guardian who is at least 25 years old. Exceptions are made for legally married couples (who must provide a marriage certificate) and active-duty military personnel. It is also important to note that while the 21-year-old can purchase alcohol, the 20-year-old cannot, and the 21-year-old is legally responsible for the minor's conduct on board. Boarding will be denied without refund if these age requirements are not met at the terminal.