Porphyrogenitism

Por`phy`ro`gen´i`tism


n.1.The principle of succession in royal families, especially among the Eastern Roman emperors, by which a younger son, if born after the accession of his father to the throne, was preferred to an elder son who was not so born.
Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.