Through generations of royals marrying each other and therefore closing the ranks of their gene pools, the Habsburg Jaw manifested itself just about everywhere in Medieval Europe. The House of Habsburg, which is named after the Habsburg Castle in Switzerland, is associated with the Habsburg Jaw because so many of its members had it.
Charles II, the last Spanish Habsburg, was feeble-minded and physically deformed as a direct result of his limited gene pool. His ancestor, Joanna of Castile, actually appears in his family tree no less than fourteen times because of first and second cousins intermarrying. It is said that Charles II's genetic makeup was more muddled than it would have been if his parents had been brother and sister.
Charles II's mandibular prognathism was so pronounced that it was said that he could not chew his food and that the size of his tongue caused him to drool significantly. He also had mental issues and was considered mildly retarded. He didn't learn to talk until he was four and couldn't walk until the age of eight. As an adult, his speech was so poor that he was, for the most part, unable to be understood.