I think you have a different concept of 'person' in mind than needed. We can define 'person' as "that which can think, reason, and has personality" or something similar (this is roughly what I think you mean by 'person'), but that isn't really relevant to the question. Like Carl said, we are looking for a value laden definition here - something to tell us whether we should use those embryos or not.

Honestly, all of this definition nonsense is misleading. We don't really care about the definition of 'person.' What we want is to sort out our values. Embryo's certainly aren't in my utility function, and that's all that matters. Defining 'person' is superfluous.