He was in prison in 2012, but his then 30-year-old son was the acting underboss for a short while around that time. The belief is that Sr is the official underboss, but some sources have Ernie Aiello as the official underboss. I am honestly not sure, but it's hard to picture Johnny Joe without an admin spot.
Jerry Capeci also had him as a Captain at one point with his son as Acting Captain a few years back before he was out of prison. It's possible Ernie Aiello is Underboss but I would believe John Spirito Sr is Underboss before I'd believe Ernie Aiello is.
Rush unless you have some info you haven't shared there has been nothing about John Spirito Sr since his release and a photo with Michael Mancuso doesn't mean we can automatically jump to him being the Acting Boss.
