This is from Royal Carribean's website
"For childern at least one year of age, we also offer individual sitting in your stateroom from 8 a.m. until 2 a.m. Rates are generally between $8 and $10 USD an hour, depending on the number of children in your family. Payments must be made in cash.
We require 24 hours advance notice and the guests can confirm the service with Guest Relations upon boarding."