Mary Henrietta of England

The daughter of Charles I and mother of William III.

Wishing to imitate the French tradition of the firstborn daughter of the King being known as Madame Royale, the French-born Queen consort wanted to do something similar for her own daughter. So, in 1642 King Charles I gave Princess Mary the title of Princess Royal, establishing a new tradition in the British Royal Family. Even as a tiny child, the new Princess Royal was immediately the center of marriage negotiations. Originally, King Charles had wished his daughter to marry into the Spanish Royal Family to secure a long-lasting alliance between Britain and Spain. His own father had tried to see him married to a Spanish princess as King James had hoped that Britain could act as the great peace-maker between the Catholic and Protestant powers as the wars between the two sides were tearing Europe apart. This was a long-standing ambition of the House of Stuart, to emerge as the monarchy that restored peace, if not unity, to Christendom. (Read entire post.)