IP mixup

Hi guys, a friend of mine has 2 laptops connected to his home network, but both laptops cannot access the internet at the same time using the wifi, however they can both connect if one or both uses LAN.

If one laptop is connected to the wifi and the other is switched on, the new one boots the previous one off the connection.

I believe the problem had sprouted from the router; which is possibly somehow giving both laptops the same wireless ip.

What can be done about this?:confused

PS
I should update with the model and make of the router soon.

 

Thanks plodr.

Just to confirm, I'm running these functions from cmd as admin.

ipconfig /release
ipconfig /renew