Wtf

how many goku are there >.>
Hypothetically, there's four, one per timeline.
First timeline: Androids kill everyone. Trunks goes back to the second timeline, and stops them. Cell comes from this timeline, as the androids are gone. .
Second timeline: Trunks warns everyone about the Androids. Androids are defeated, Cell doesn't come back.
Third Timeline: Androids kill everyone. Trunks goes back to the fourth timeline, Meets cell, and prevents him from going back. This is the future we usually know.
Fourth Timeline: Main timeline.
If Black Goku doesn't exist because of the timetravel, then there should be one in each, although the Second timeline is most likely the one we're dealing with.