I am not a descendant of General Francisco de Miranda, but because I carry the surname Miranda, I am always being asked if I am and also being told that there is much information to be found on him and his genealogy.
I don't know if you have any large libraries near you, but if you do, I would try searching their card catalogs to see if they have any books about him/his genealogy. I live in New York and I did a search of the New York Public Library (the research library)card catalogs online and came up with a lot of books about him.
If not, the Family History Library has microfilm titled "El precursor Miranda y su familia : primera biografía general de la familia de Miranda" (Film #1162485) which discusses this family. You can find the Family History Center closest to you (they have locations all over the world) and order the film, then view it at their center. You can locate the Family History Center closest to you by doing a search at their web site which is here: