And if one person holds coins in bitcoin before 2017 doesn't the same person hold coins in BCH?
If you hold btc from the time that btc was forked during 2017 then yes the same private keys and addresses that hold your btc will be the same as the ones you hold bch with. You hold the equal amount of btc and bch and I think that you can claim your bch with your btc private keys as long as you have bch wallet.