(details from "Maria Anna or Mariana de Austria, Reina y consorte de Felipe IV ") Diego Rodriguez de Silva y Velazquez (1599-1660) Kunsthistorisches Museum, Vienna, Austria

Her son Carlos II inherited her mutated H+ gene, as well as the same mutated gene from his father Felipe IV. ("double hit") - the implication is that those who inherit two H+ lack a normal gene - probably one reason for the increased likelihood of their demise or of having much more severe developmental anomalies than those who inherit only one H+ causing gene. More about "double hit" H+, please see entries concerned with Carlos II and Carlos de Asturias and entry pages concerned with these princes.