There is no "I" in "You"

[quip]

What determines "my parents";

The owners of the sex organs from which you were produced, in most cases.

Correct, though I'm referring to "you" prior to conception. 

"my sensory system"...etc in relation to yours prior to either of our extant circumstances?

There is no me and you or us to compare or contrast "prior to our extant circumstances".  The question is nonsensical in context.  Rephrase?

Perhaps, that's where science may fall short. QED