Pareja was enslaved in Velázquez's workshop, was later freed, and became a painter in his own right. When this portrait was shown in Rome in 1650, it was said that everything else looked like painting, and this alone like truth.
Shop / Juan de Pareja

Juan de Pareja
Velázquez · The Metropolitan Museum of Art
Velázquez (Diego Rodríguez de Silva y Velázquez), 1650. The Metropolitan Museum of Art, Open Access (public domain).