Sharing between 2 people on the same IP address who play on the same server is done by design and isn't against the rules. It looks like he was implying this guy was misusing his key, which would be the case if it was "shared from different locations." Since they are both on the same server at the same time, though, the former would be the case and there isn't really a problem here.
Two IP's can't be the same, even in the same house.
There is a rare porability of that to happen, but that's not the chance here.
Indeed, the IP's in the same house are very close. But they have a difference by 1 number or more, based on the Internet Service Provider.