Look at what I just read in Stanford Encyclopedia of Philosophy: "2. You could not have been born of different parents. (Someone born of different parents wouldn't be you.) (...) Each of these claims appears to have a true reading."
Do you all think this way? A son of my paternal twin-uncle and my maternal twin-aunt could easily (so to say) have exactly the same DNA as I have. He could have been born on the same day. He could have been told that his parents were my actual parents. He could have been given my name. My actual parents could have had no biological child. Things in the whole world could have been exactly as they actually were and are since then. So, in what reasonable sense wouldn't this person be me?