Fox or BB or Venoms?
Solid Snake went to salute "Big Boss," whose grave was located right next to the Boss'. It's really not that hard to grasp.
Although Venom was probably buried there instead of the real Big Boss.
Is the guy that makes Venom's bionic arms really Madnar?
BB, Solid Snake pretends John didn't had an impact in him, but killing him was actually a really big hit on his life. Making him suffer PTSD, and depression, but at least in the end of his life BB and him fixed all their problems and went in peace