In the later 10th-century, while nominally in vassalage to the Kingdom of León, the counts grew in autonomy and played a significant role in Iberian politics.
After the assassination in 1029 of Count García Sánchez of Castile, King Sancho III of Pamplona, because of his marriage to Muniadona, García's sister, governed the county although he never held the title of count:[1] it was his son, Ferdinand Sánchez, the future King Ferdinand I of León who inherited the county from his mother.
[2] Near the end of 1063,[a] Fernando I convened the Curia regis to announce his testamentary dispositions pursuant to which he had decided to divide his dominions among his sons.
[14] Al Andalus sources referred to the family as the Beni Mamaduna, the descendants of Muniadona de Lara [es], Fernán's mother.
Sancho thus became de facto ruler of Castile, though he was never its count,[1] nominating his younger son to succeed Garcia.