Berengaria of Leon was the third wife but only empress consort of John of Brienne, Latin Emperor of Constantinople
Berengaria was a daughter of King Alfonso IX of León and Queen Berengaria I of Castile. She was a younger sister of Ferdinand III of Castile and Alfonso of Molina.
Their paternal grandparents were Ferdinand II of León and Urraca of Portugal. Their maternal grandparents were Alfonso VIII of Castile and Eleanor of England.
In 1217, Berengaria's brother Ferdinand III had inherited the throne of the Kingdom of Castile through abdication of their mother.
In 1223, John of Brienne, aged 53, visited Santiago de Compostela, as a supposed pilgrim. He was by then twice a widower: first, in 1213 of Queen Maria of Jerusalem and then of Stephanie, daughter of Leo II of Armenia.
As a consequence of his visit to Santiago de Compostela, Alfonso IX invited him to marry Sancha and, presumably, through her inherit the Leonese throne.
However Berengaria of Castile, a long time divorced and an inheritor in her own right of the Castilian throne, main advisor of her son Ferdinand III, offered one of her own daughters to John instead.
Aging John chose Berengaria of Leon, from Alfonso IX's second doomed marriage, who was a decade younger than her half-sister Sancha, from Alfonso IX's first doomed marriage.
The marriage took place at Toledo in 1224.
Berengaria and John of Brienne had four known children, known to have been residents in Spain with his cousin, King Alfonso X of Castile, signing widely in many documents for many years with other high nobility witnesses, Bishops and Archbishops, Royal legitimate and illegitimate offspring and so on :
Marie of Brienne (1225-1275), who married Emperor Baldwin II of Constantinople.
Alphonso of Brienne (c. 1228-1270), who married Marie d'Issoudon, countess of Eu, and became count of Eu in right of his wife, and was also Great Chamberlain of France. Died of a plague while involved in the Eighth Crusade.
John of Brienne (c. 1230-1296), who in 1258 became Grand Butler of France. Married Jeanne, Dame de Chateaudun, daughter of Geoffrey VI, Viscount de Chateaudun, as his first wife. His second wife was Marie de Coucy, widow of King Alexander II of Scotland.
Louis of Acre (c. 1235-1263), who married Agnes of Beaumont and became Viscount of Beaumont in her right.

Berengaria of Leon was the third wife but only empress consort of John of Brienne, Latin Emperor of Constantinople
Berengaria was a daughter of King Alfonso IX of León and Queen Berengaria I of Castile. She was a younger sister of Ferdinand III of Castile and Alfonso of Molina.
Their paternal grandparents were Ferdinand II of León and Urraca of Portugal. Their maternal grandparents were Alfonso VIII of Castile and Eleanor of England.
In 1217, Berengaria's brother Ferdinand III had inherited the throne of the Kingdom of Castile through abdication of their mother.
In 1223, John of Brienne, aged 53, visited Santiago de Compostela, as a supposed pilgrim. He was by then twice a widower: first, in 1213 of Queen Maria of Jerusalem and then of Stephanie, daughter of Leo II of Armenia.
As a consequence of his visit to Santiago de Compostela, Alfonso IX invited him to marry Sancha and, presumably, through her inherit the Leonese throne.
However Berengaria of Castile, a long time divorced and an inheritor in her own right of the Castilian throne, main advisor of her son Ferdinand III, offered one of her own daughters to John instead.
Aging John chose Berengaria of Leon, from Alfonso IX's second doomed marriage, who was a decade younger than her half-sister Sancha, from Alfonso IX's first doomed marriage.
The marriage took place at Toledo in 1224.
Berengaria and John of Brienne had four known children, known to have been residents in Spain with his cousin, King Alfonso X of Castile, signing widely in many documents for many years with other high nobility witnesses, Bishops and Archbishops, Royal legitimate and illegitimate offspring and so on :
Marie of Brienne (1225-1275), who married Emperor Baldwin II of Constantinople.
Alphonso of Brienne (c. 1228-1270), who married Marie d'Issoudon, countess of Eu, and became count of Eu in right of his wife, and was also Great Chamberlain of France. Died of a plague while involved in the Eighth Crusade.
John of Brienne (c. 1230-1296), who in 1258 became Grand Butler of France. Married Jeanne, Dame de Chateaudun, daughter of Geoffrey VI, Viscount de Chateaudun, as his first wife. His second wife was Marie de Coucy, widow of King Alexander II of Scotland.
Louis of Acre (c. 1235-1263), who married Agnes of Beaumont and became Viscount of Beaumont in her right.