There are Mendoza families in Spain with different origins. It is true that
one of those families was, and is, one of the most prominent of Spain (that
of the Dukes of the Infantado - the palace in Guadalajara is called "Palacio
de los Duques del Infantado"), Marquis of Santillana and several other
titles. To that family belonged don Antonio de Mendoza, 1st viceroy of New
Spain. I don't recall at this point their connection(s) with the Spanish
royalty (but I'm certain that there are several) and it is true that the
ancestry of the Spanish royal family can be traced back to Pedro, Duke of
Cantabria, who lived in the VI century.

>From: mormonboy74
>Reply-To: research@nuestrosranchos.org
>To: research@lists.nuestrosranchos.org
>Subject: [Nuestros Ranchos] The Mendoza Family in 1500's Mexico
>Date: Wed, 9 May 2007 22:45:44 -0700 (PDT)
>
>
>I heard the Mendoza family comes from a long line of Castilian Nobility is
>this true? There were dukes, counts, lords, princes, etc. They also owned
>the Guadalajara Palace of Mendoza and descend from Fernando I? Is all this
>true. I found websites that have this genealogy for the Mendoza familiy
>going back to 500 A.D.