When Your Sister Has a Sex Tape...

...it's gotta be the last thing on Earth you would ever wanna see -- but when we found Kim Kardashian's brother in Beverly Hills yesterday, we asked him about it anyway.
Robert Kardashian: Click to watch
Robert should praise Jebus Reggie Miller happened to walk by -- 'cause that was the only reason he got out of the most obscenely awkward sex conversation ever.