Bourbon no Fuuin

Overview

James, handsome, well-educated, and brilliant, is the adopted son of a family prominent in the English aristocracy. James is curious about his origins and wants to know why he was abandoned. Unknown to James, he is the son of the former King of France, Louis XIII, and the elder brother of King Louis XIV. In fact, James and the present king are twins. Louis XIII could not have children for a long time. When finally he had a baby boy he immediately announced that a prince, the heir to the throne of France, had been born. But just after this a second boy was delivered and in the case of twins the second one born is considered older than the first. The king thought it would be a bad omen if he had to announce a different heir...

Source: AniList