The son of Philip II and Elisabeth of Valois

OTL, Elisabeth of Valois, third wife of Philip II, king of Spain, died due to the miscarriage of her son. WI she had a normal pregnancy, and the boy is healthy? Philip then don't need to marry his niece, Anna of Austria, to have an male heir, and another round of the "Habsburg interbreeding" doesn't happen.
 
Born 1568, the boy has become a young adult when Henry III of France gets murdered.
Henry of Navarre has a much harder time.
 
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