1CK6KHY6MHgYvmRQ4PAafKYDrg1ejbH1cE I believe is an old block chain address of mine
An address cannot 'belong to someone', but you could be in possession of the private key which allows you to spend from it. So if you have the private key (ie, you have access to the wallet that created that address, or a backup of it), then you can claim any coins held at that address.
Thats a Legacy Key, long Time ago they where the only ones wich you could Verify Transactions. Soon they gonna Veanish complete and the bech32 Keys will be Master.