It's the same for any category, except, of course, that the rates are different.
Regardless of age, there's 1st/2nd passenger rate (sometimes mistakenly called an adult rate) for the 1st and 2nd passengers sharing a stateroom, based on double occupancy.
Then, there are three age-based rates for 3rd, 4th, and 5th passengers (up to the capacity of the stateroom). The appropriate 3rd/4th/5th passenger rate kicks in after the first 2 people at the 1st/2nd passenger rate:
- Under age 3
- Ages 3-12
- All other
This is significant because the 13-and-over "all other" (adult) rate for a 3rd/4th/5th passenger is lower than the 1st/2nd passenger rate. In fact, it's significantly lower in the more expensive categories.