In 1621, Anthony van Dyck traveled to Italy. He was only twenty-two, but he considered himself a man of consequence. As a student of Rubens he had become accustomed to the contact with royalty, he had been invited to England, King James had given him £100. He wore silks, a hat with feathers and brooches, gold chains across his chest, and was accompanied by servants. He annoyed the rather bohemian Northern artist’s colony in Rome no end, but so what? He spent most of the time in Genoa anyway.
Also in 1621, Alessandro Ludovisi was elected pope, he called himself Gregory XV. The Republic of Genoa appointed Agostino Pallavicino ambassador to the new pope, the scarlet robe is a sign of this position, he was not a cardinal. If the portrait was made at the time of his appointment, it was among the first things Anthony van Dyck painted in Italy. It is at the J. Paul Getty Museum now and has a nice description page at their website.
In 1637, Agostino would become Doge of the Republic of Genoa, the first Doge from the Pallavicini family. Unfortunately I could not find out how he was related to Nicolò.