Answer
The Battenbergs were a morganatic branch of the House of Hesse-Darmstadt. They were descended from Louis, Grand Duke of Hesse, and his mistress, Countess Julie von Hauke. The couple were married in 1854 in a civil ceremony, but the marriage was not recognised by the Church and the children were born illegitimate. In 1857, Louis gave his wife and children the title of Prince and Princess of Battenberg.