In the filler arc G-8 Jonathan was mentioned to be Red Dog's Protege. He was called by two titles though, commander and vice admiral, so I'm not sure which one he is. However he does command G-8 and in Aces side story G-2 was commanded by another vice admiral as well.
Now this arc is filler but calling him the protege of Akainu seems kinda of risky by Toei.
Do you think Toei ask Oda if they are allowed to do this? I mean it seems pretty big…
If Oda agreed do you think he is going to somehow pop up again in the manga? Its unlikely but still I thought being the protege of someone, especially an Admiral is pretty impressive.
We didnt get to see him in action. However, in one scene its hinted by Sanji he is probaly very powerful.
I don't know if theres a thread for this, I searched with the word Jonathan but couldnt find anything.
Just in case you guys dont remenber who he is or didnt watch the arc http://en.wikipedia.org/wiki/One_Piece_filler_characters and just look for Jonathan.