Japanese voice actor Chikao Ōtsuka passed away at age 85 yesterday, on January 15th. He was the father of Akio Ōtsuka, who has been voicing Snake since Metal Gear Solid 1 (and currently Big Boss in The Phantom Pain).
Chikao Ōtsuka (1929 – 2015)
For Metal Gear Solid 4, Chikao Ōtsuka joined his son in the recording booth to voice Big Boss, paralleling the father-son relationship in the story.
Source: Anime News Network, via V T A K on Twitter