>>719939936
Eva was just the surrogate mother and shares no genetic link to Snake. The old backstory is that Big Boss has Japanese ancestry in some manner, but this is either forgotten about or dropped.

The English MGS official guidebook took some of the canon plot points and then created a fan-fic biography based off of them, and actually wrote a more interesting backstory than what Kojima gave him. I bet you anything they never thought that Big Boss, who was dead, was ever going to ever appear in a sequel, so none of this mattered.