|The point of a SOHO Router is to allow multiple LAN computers to access the internet through a single non-private IP address.|
If both of your clients are using DHCP to get their TCP/IP settings from your router, they cannot have the same IP.
Besides, the way IPv4 is setup it's impossible to have two computers use the same IP so I don't know what you are talking about.
What exactly has the same IP address?
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.