Maria of Montferrat in the context of Isabella I of Jerusalem

John of Brienne (c. 1170 – 19–23 March 1237) was the king of Jerusalem from 1210 to 1225 and Latin emperor of Constantinople from 1229 to 1237. He was the youngest son of Erard II of Brienne, a wealthy nobleman in Champagne. John, originally destined for an ecclesiastical career, became a knight and owned small estates in Champagne around 1200. After the death of his brother Walter III, he ruled the County of Brienne on behalf of his minor nephew Walter IV, who lived in Italy.

The barons of the Kingdom of Jerusalem proposed that John marry their queen, Maria. With the consent of Philip II of France and Pope Innocent III, he left France for the Holy Land and married Queen Maria; the couple were crowned in 1210. After Maria's death in 1212 John administered the kingdom as regent for their infant daughter Isabella II; Maria's influential uncle, John of Ibelin, attempted to depose him. King John was a leader of the Fifth Crusade. Although his claim of supreme command of the crusader army was never unanimously acknowledged, his right to rule Damietta (in Egypt) was confirmed shortly after the city fell to the crusaders in 1219. He claimed the Armenian Kingdom of Cilicia on behalf of his second wife, Stephanie, in 1220. After Stephanie and their infant son died that year, John returned to Egypt. The Fifth Crusade ended in failure (including the recovery of Damietta by the Egyptians) in 1221.

Isabella II (Old French: Ysabel; 1212 – May 1228), sometimes called Isabella of Brienne and erroneously Yolanda, was the queen of Jerusalem who reigned from 1212 to 1228. She was the daughter and successor of Maria of Montferrat, who died shortly after giving birth to her. Like her mother, Isabella died young before she could make an impression on politics.

Isabella's father, John of Brienne, ruled during her long minority; while he continued to regard himself as king for life, his opponents insisted that he was merely regent for Isabella. In 1223 John arranged for her to marry Emperor Frederick II, king of Sicily. A proxy wedding was held in the Kingdom of Jerusalem in August 1225, followed by Isabella's coronation as queen of Jerusalem. She then promptly departed for the Kingdom of Sicily, where she married Frederick in person. The marriage made her queen of Sicily and empress of the Holy Roman Empire. Defying his agreement with her father, Frederick declared himself king of Jerusalem immediately after their wedding and seized control of her kingdom. He sidelined Isabella, whose role in government was minimal. Her father's supporters alleged that Frederick abused her. She died shortly after giving birth to her only son, Conrad II, who succeeded her under Frederick's tutelage.

John of Ibelin (c. 1179 – 1236), called the Old Lord of Beirut, was a powerful crusader noble in the 13th century, one of the best known representatives of the influential Ibelin family. The son of Balian of Ibelin and the dowager queen Maria Comnena, he had close ties with the nobility of both Cyprus and Jerusalem, since he was the half-brother of Queen Isabella I of Jerusalem. Before he was 20, he was appointed constable of Jerusalem, and a few years later became Lord of Beirut. John rebuilt Beirut after Saladin's conquest, and established the grand Ibelin family palace. He served as regent of Jerusalem on behalf of his niece Maria of Montferrat from 1205 to 1210 after her mother, Queen Isabella, died. He was also regent for his great-nephew (Isabella's grandson) Henry I of Cyprus from 1228 until Henry came of age in 1232. John was known as a principled man, and was seen as the natural leader of the Christian barons in the Holy Land. He resisted the power-seeking of Frederick II, Holy Roman Emperor, in Cyprus, and opposed the imperial forces until King Henry came of age.