Dude i will explain nice and easy for you
Each Router has 1 IP
NOT MORE NOT LESS therefore
sharing the same
IP
even if another PC joined the wifi it will have the same ip no matter what (unless you use proxy)
Also if you mean to ban the PC only (if that is possible)
I know some people that share PC as 1 pc per family or 2
so if you are sharing you ban everyone who uses that PC
Also as
@FalseHonesty Said
If you IP Ban you can ban an entire school household, library, etc
Finally the best a mod can do is this
Check the IP of the hacker
go check any player who has the same IP
and watch the player