What if Philip IV of Spain's son, Balthazar Carlos survives?
Balthazar was a healthy child from Philip IV's French wife Elisabeth of France. If he lived, the Spanish Hapsburgs would last longer under the alternate Carlos II. There is one problem that Balthazar was going to marry his cousin Mariana( yes the future Queen of Spain) but you could either get healthy kids out of them (rather unlikely genetically) or have her die in childbirth. What effects would this scenario have?