Okay, here's an idea: Kazuhira Miller and McDonnell Miller are two different people. Here's my reasoning:
- They have different names.
- McDonnell Miller was a survival expert who helped train Solid Snake, but, as evidenced by MGSV trailers, Kazuhira Miller has lost his eyes, an arm, and a leg. While prosthetic limbs are abound in the universe, fake eyes are not (otherwise why would Big Boss still have an eyepatch?).
- There is clearly a different person voicing a Miller looking guy at the beginning of the trailer where Big Boss is said to be in a coma, and Robin Atkin-Downes (the voice of Kaz) is in that trailer in different spots.
- Kaz has said before that he did not live with his father while growing up, and thus he could easily have a brother who looks just like him, but they never knew each other until later in life.
Okay, so what does everyone else think?