Inbreeding has been the custom of ruling dynasties for thousands of years; mostly it was due to a desire to keep the bloodline "clean". In the age of Versailles marriages were made to form alliances with other European powers.
Louis XIV and Marie Thérèse were first cousins and as such were the closest relations of the three kings and their consort inhabiting Versailles. Anne of Austria - mother of Louis XIV - was the sister of Philip IV of Spain; he happened to be Marie Thérèse's father.
Louis XV and Marie Leszczynska were not related by 18th century standards. Neither their parents nor their grandparents were related by blood. As such the chose of the Polish princess as a bride was a good choice in more than one sense: first, it enabled the king to produce an heir immediately, secondly, it angered none of the other powers and thirdly, it brought in "new blood".
Louis XVI and Marie Antoinette were related but not closely. Marie Antoinette was the daughter of Francis I, Holy Roman Emperor who in turn was the grandson of Philippe, Duc d'Orléans (Monsieur) and Elizabeth Charlotte of the Palatinate.
|Louis XIV meeting the king of Spain (his uncle) and his bride (his cousin)|
The Dauphins and Dauphines
Louis, the Grand Dauphin and his bride, Marie Anne Victoire of Bavaria, were second cousins. The Grande Dauphine's grandparents were the Duke of Savoy and the French princess, Christine Marie (a sister of Louis XIII).
The Duc and Duchesse de Bourgogne were also second cousins. Marie Adélaide of Savoy's grandfather was Philippe, Duc d'Orléans (Monsieur). Ironically, her great-grandparents were Christine Marie of Savoy and Victor Amadeus - the parents of the Grande Dauphine.
Louis Ferdinand and Marie Thérèse Raphaëlle were also rather closely related. Actually, this short-lived Dauphine was a direct granddaughter of Louis XIV himself through the second son born to the Grand Dauphin.
|Wedding of the Duc and Duchesse de Bourgogne - the Duc d'Orléans is|
depicted as well; a common ancestor of the couple