If you're just looking for basic info, can you run those sources through google translate?
Just out of curiosity, have you TRIED doing that? With Spanish (which I don't speak or read), I have as much luck understanding it by pretending it's bad French/Latin as by reading the 'translation' Google gives me.
I was being imprecise in my statements, it would appear.
More accurately, it should have read. I am finding it hard to find any good sources, and those sources I find (which are in Spanish) are mostly genealogies that tells nothing of what property these families owed, what their political views, connections and aspirations were, whether they were involved in administration, etc.
They basically just go "Family X, founded when King Y made Z a nobleman. Roots originally in region W of old Spain. List of people having the title of Duke/Count/Marquis/Viscount of X."
The only family I have actually been able to find anything more on (and where there is no lack of information in English) is the House of Iturbide, and I would like to be able to use another family than the first Imperial would-have-been-dynasty.