My laptop keeps disconnecting my home connection

I don't understand why. Everytime my stepdad puts his laptop on, the internet gives out on my home computer. The entire network just disconnects. The SSID doesn't even show up on the laptop when i refresh the network listing. I put the laptop right next to the router and it still didn't detect anything. Every once in a while, it WILL work . . but only for like 5 mins and it sometimes says the connection is "EXCELLENT" . . but won't even load a page. It's just really weird. I hope you guys can help. I believe the issue is with the wireless router because i connected it to the modem and it worked perfectly fine.