He was the son of don Diego de Haro, marquis of Carpio, and of doña Francisca de Guzmán, sister of count Olivares. He made a career at the Spanish court under protection of his uncle, whom he succeeded as valido or favourite in the king's confidence when Olivares was driven from office in 1643. He never achieved the same influence and control as his uncle, mainly because Philip IV also relied on Sister María de Ágreda. She convinced the king to abolish the function of valido.