Eleanor of Aquitaine is better known for her second marriage, to England's Henry II. But before she was married to Henry, she was queen consort of France's King Louis VII. When their first daughter, Marie of France (later Countess of Champagne), was born, the marriage was already in trouble; the later birth of a second daughter, Alix of France, was as good an excuse as any to end the marriage and let Louis try to find a wife who would bear him sons. But Eleanor went on to have famous sons and daughters, and Louis finally had a son during his third marriage.
Marie and Alix were left in France in their father's custody, and later were married to brothers of Louis' third wife. Marie spent quite a bit of her married life serving as regent, first for her son and then her husband. She's assumed to have inspired, as well, a famous book, known in English as The Art of Courtly Love, likely written by her chaplain. But she's not the same 12th century Marie of France who wrote books in the courtly love tradition. Read more about this first child of the powerful Eleanor of Aquitaine: Marie of France, Countess of Champagne