Interesting question! It depends on what you mean by being “someone” in the first place.
Identical twins have the same genome but are not the same person, right?
We could change a person’s genes to, say, cure their disease, but I don’t think they’d be a different person, they’d be the same person but without the disease. It depends on how much you consider a particular gene to define who that person is I suppose! https://www.sciencemag.org/news/2017/11/boy-rare-disease-gets-new-skin-thanks-gene-corrected-stem-cells