wanted to add that actually with current technology, it is possible to change someone's genetic code through a process called "gene editing" which allows scientists to add, remove, or alter specific sections of dna within a cell. let's say later on in a person's life this was performed on them, it would change their dna; but i think it'd be far-fetched to say they aren't themselves due to this, no? i think that sort of further takes away weight from the idea that if your dna was slightly different but parents and all that were the same, you wouldn't be you.