Casey Affleck is turning documentarist. He’s teaming up with Joaquin Phoenix to do a behind-the-scenes look at his new life as a musical artist. As you may recall, a few months ago, Joaquin announced that he was done with acting, and wanted to focus solely on music. But what may surprise you is that Phoenix is a rapper! We kid you not. Diddy is even producing his album. He’s even making his first public appearance tonight in Vegas with a performance at a club. So why these two? Well what you may not know is that Casey and Joaquin are actually brothers-in-law. Casey is married to Summer Phoenix, who is Joaquin’s sister. We already know Joaquin can sing, based on his amazing portrayal of Johnny Cash in Walk the Line. But rapping is a whole other story. Maybe he’s the next Eminem? We’ll have to wait and see!