Shortly before Isabella's birth, her mother was dealing with problems in Castile, involving her brother John I of Aragon.
Eleanor was forced to return to Navarre for her daughter's birth.
Her two younger brothers died in childhood, leaving Isabella and her five older sisters.
Her sisters included: Joanna (died before inheriting the throne), Blanche (successor of their father), and Beatrice.
[3] John later became King of Aragon but broke off his contract with Isabella, in hopes of marrying Joanna II of Naples.