Step-by-step explanation:
Isabella was the daughter of John II of Castile and his second wife, Isabella of Portugal. Three years after her birth her half-brother became king Henry IV. Even though she had a younger brother, Alfonso, and her early years were spent quietly with her mother at Arévalo, Isabella was soon drawn into Castilian politics. She was brought to court when she was 13 to be under the king’s eye. At first, the opposition to Henry IV gathered around Alfonso, but when the latter died in July 1468, the rebellious magnates naturally turned to Isabella. She did not, however, play the role thus designed for her, and the fruit of her wisdom was recognition as his heiress by Henry IV at the agreement known as the Accord of Toros de Guisando (September 19, 1468)