Eleanor of Aquitaine was a teenager, a bit of a handful, beautiful and wild and, when her father died in 1137 leaving her the entire duchy of Aquitaine, the richest 15-year-old in France. She was immediately placed under the “protection” of the crown and pledged in marriage to the newly-crowned King Louis VII.
Louis had been raised to be a monk but when his older brother died, he ended up king. And as the saying goes “you can take the boy out of the monastery, but you can’t take the monastery out of the boy” (except the saying went in French). As a result, Eleanor was rather disappointed in the consummation department. She is quoted as saying “I thought I was wed to a king, now I find I am wed to a monk.” To show her pique, she gave Louis no son and heir.
Fifteen years passed, and Louis became convinced that God was punishing him for marrying a third cousin once removed. A church court consulted a dusty rule book and found a convenient grounds for annulment — a third degree of consanguinity, marrying a third cousin once removed. (In case you were wondering, there were seven degrees.) The court granted an annulment on March 24, 1152.
Bye bye Eleanor and bye bye duchy of Aquitaine, making it the most expensive divorce ever. Louis remarried and eventually got a son. Eleanor quickly got herself another monarch, Henry II of England.
Wretched Richard's Almanac 