A question I've been pondering recently is, what might've happened had the House of Valois survived past 1589, either through Henry III having a son, or some other legitimate son of Henry II and Catherine De Medici surviving and having issue?
Would the French wars of religion continued? Could we see an Edict of Nantes happen earlier?
Who is the best candidate for a surviving House of Valois? Francis II, Charles IX, Henry III or perhaps their brother Louis of Valois who otl died in 1550, but if he were to survive, what might happen from there?