Often used in the context of literature, especially in relation to Don Quixote.
El sancho de Don Quijote siempre estaba dispuesto a ayudar a su amigo en todas sus locuras.
Don Quijote's squire was always ready to assist his friend in all his craziness.
El valiente sancho siempre estaba al lado de su caballero.
The brave squire was always by his knight's side.