Luís was born in the city of Porto, on 6 October 1630, since is father was the Governor of the "Relação e Casa do Porto", hereditary rank given to his family in 1582 by Philip II of Spain, the new king of Portugal after the Iberian Union. In 1633, Diogo de Sousa was appointed chairman of the "Conselho da Fazenda" by Philip IV and the family moved to Madrid. The young Luís entered in the household of queen Elisabeth as a page until 1646, when his family was allowed to return to Portugal after the revolution of 1640.