There are no infant rates on RCI - they will pay the 3/4 passenger rates. Babies not allowed under 6m old any more. Children rates (where they exist) is up to 11 yrs - over that is an adult, but again they usually end up paying 3/4 passenger rates.
Sorry to counter your response Aldrich but here's a piece off RCI.com & I've just phoned RCI in Weybridge to confirm it's still current. The age is up to 12yrs for a child & they confirmed it's available for all cruises. I didn't ask about the 'Very' young though, but there was a 'Few week old' babe in arms on Navigator last week. See you on the 27th Regards
*Minimum unaccompanied minor age is 21 or older; no guest under the age of 21 will be reserved in a stateroom unless accompanied by an adult 21 years or older. This age limit will be waived for minor children sailing with their parents or guardians in adjacent staterooms or for under age married couples (proof of marriage is required). In the case where two parents or adults are traveling with minors, (more than one stateroom) RCI strongly suggests that both parents or adults be booked on the same deck, with cabins adjacent or in the same vicinity. Royal Caribbean reserves the right to ask for proof of age. *Please note: an individual's age on the date of sailing determines his or her status for the entire cruise vacation. Royal Caribbean International does not accept bookings for student groups. Infant age range is 0-35 months. Child age range is 3-12 years. Adult age range is 13-54 years.
Infant is up to 3 years old. Child is 3-12 years old. Bear in mind the rates are reduced regardless of age for 3rd & 4th passengers in one cabin.