Sonny did have a crew. Smaller than Tessio and Clemenza. From the novel Don Vito had territory in the Bronx (Clemenza), Brooklyn (Tessio), and Manhattan which that capo was never identified. We are never told who all the capos are, only that Tessio and Clemenza were the old guard who Don Vito trusted. Vito making his son Sonny from Soldier to Underboss would be egotistic which Vito was not. So it stand to reason that Sonny was a young capo he was born in 1916, before he became underboss to his father. In the book we know Michael with Vito's support and blessing made Rocco Lampone capo was bolstering that caporegime secretly making it the most powerful in the family. Al Neri, I have seen posted as a Capo, but he was direct with Michael and had no one under him in a crew. He was in fact Michael's Luca Brasi, and could do more than what Brasi could do.

Glad I found the book, I was wrong, Al Neri took over Tessio crew. Rocco Lampone is a capo and considered Michael most trusted Capo. Only Barzani and Tattaglia are killed.