I haven't studied philosophy, so I may be naive here, but does this question NOT depend on the definition of "right"? In a practical discussion, maybe both parties would agree that "right" in this case means "fair, in accordance with my contributions to this startup".
But in a philosophical debate, "right" would be quite ambiguous. One party, for example, could posit that the ideas of "right" and "wrong" are completely subjective. That, in the absence of some stated goal or constraints, what's "right" or "wrong", "good" or "evil" is no more valid a topic of debate than whether chocolate ice cream is better than vanilla. However, once you introduce said constraints, the discussion is no longer philosophically interesting.