They were both traded within minutes of each other too. I also think it would be interesting at some point if brothers were traded for each other. It happened earlier this month in the NBA with the Gasols.
I was kind of surprised reading a player could be traded for himself so I had to look it up. It was true. Happened twice actually. I would image something like this would have to be against the rules now.
In April, the Mets traded catcher Harry Chiti to the Indians for a player to be named later. On June 15, the Mets received the PTBNL, who turned out to be Chiti, making Chiti the first player to be traded for himself (in 1987, in the same sort of scenario, Cubs pitcher Dickie Noles was also traded for himself).