[Marriage of Isabella of Jerusalem and Humphrey of Toron, 13th century, source:
Isabella was the daughter of Almaric I of Jerusalem and Maria Komnene. Though her father’s previous marriage had been annulled, her half-siblings Baldwin and Sibylla were considered legitimate and were ahead of her in line for the throne. Since Baldwin had contracted leprosy and it was unexpected that he would have children, Sibylla became his heir, though there were some who wanted to contest her legitimacy and put Isabella on the throne.
A few nobles actually tried to do this, but Isabella’s first husband, Humphrey of Toron, would have none of it. The pair had been betrothed when she was 8 and he 14. They married three years later. Instead of trying to take the throne though, Humphrey, who did not want to be king, did homage to Guy of Lusignan, Sibylla’s husband, recognizing him as his lord.
When Sibylla died in 1190 and Guy refused to give up his crown, Maria insisted Isabella find a new husband who could take it back for her. Isabella next married Conrad of Monferrat and the pair were acclaimed King and Queen of Jerusalem. But it didn’t last long. In 1192 Conrad got himself stabbed to death, leaving Isabella pregnant with a daughter, Maria.
Isabella chose to remarry very quickly, this time to Henry II of Champagne, who was closely connected to the kings of England and France and was politically a fantastic match. The marriage only lasted three years though and ended when Henry fell out a window and died, leaving her with three more daughters.
She last married Almaric of Cyprus, Guy of Lusignan’s brother by whom she had two daughters and a son, who died in infancy. They ruled together for seven years, dying days apart from each other in 1205. Isabella's thirteen-year-old daughter Maria succeeded them as Queen.
Isabella of Jerusalem - Epistolae
Queens Regnant: Isabella I of Jerusalem - History of Royal Women