Grandees of Spain are of two sorts, this Honour being sometimes personal, sometimes hereditary. The first, the King bids be covered themselves; the second, themselves and Heirs for ever. This is all the Ceremony in making a Grandee, neither do any other priviledges belong to it; so that it is but a Chimerical and Airy Honour, without any profit; they which marry the Heiress of a Family of a Grandee of Spain, that is such hereditarily, become Grandees in right of their Wives.
Source: wiktionary