It appears the O’Sullivans may be the oldest documented royal family on record, according to Mr. McCreight in Part I of his book, “O’Sullivan History.” He builds the case with plenty of cited sources as he follows the family from Ireland back to Spain and France. He details the O’Sullivan clan in historical times with accompanying photos of some very old castles, which he names and briefly describes, some with supplementary drawings depicting how they looked intact centuries ago.
Part II is the O’Sullivan Genealogy documenting six major O’Sullivan genealogical lines of the Mór, Beare and MacCragh septs. He uses the New England Historical & Genealogical Register format, outlining six parallel Sullivan lines descended from a common O’Sullivan ancestor down 31 generations.
It seems to me if you have the O’Sullivan or Sullivan surname in your genealogy, you’d like to take a look at this book.
O’Sullivan (Ó Súillebháin) The Earliest Irish Royal Family History and Genealogy is available from the publisher, Genealogical Publishing Co., athttp://www.genealogical.com/products/OSullivan/8355.html as well as from Amazon at http://goo.gl/lV0est and from many other genealogy bookstores.