A steward is a position within Castle Daventry. Daventry has a number of stewards. Rosella borrowed a faded shirt from one of the stewards of Castle Daventry to help put together her lassoing outfit.
Behind the scenes[]
A steward is an official or minister who is appointed by the legal ruling monarch to represent them in a country, and may have a mandate to govern it in their name; in the latter case, it roughly corresponds with the position of viceroy (for Romance languages), governor, or deputy (the Roman rector, praefectus or vicarius). It was also a term used to refer to the chief servant of a landed estate. Compare with Seneschel.
In King's Quest sense it appears to be a position below the Seneschel and probably within servants that the seneschal is charge of (perhaps like a butler). It is not clear if they have any representative, governing, legal, or civil duties in the kingdom.