Imagine that you and I are sitting at opposite sides of a table in a restaurant. I may confidently declare that I am here and you are over there. You may claim exactly the same thing, even although your here is my there and vice versa. Yet there is no inherently existing here or there for either of us. My here only exists in relation to you, and your here can only function in relation to me. Nevertheless, we are both factually correct in the context of the spatial relationship of our seating positions at the table.
We would be mistaken in asserting that here does not exist at all, and astute to acknowledge that my here and your here exist only in dependence on connected factors and specific conditions. Similarly, our sense of self persists only in relationship to each other. While there is no doubt that I exist and you exist as entities; it cannot be denied that in many important respects that I only exist because you exist.
It would be curious to observe the ways in which our learned sense of selfhood altered, if either of us somehow became the only being in our universe.
Every cell in our body changes every seven years. Where is identity located ?