Using two Wifi with one Cable modem

How to connect two Wifi AP to a one internet connection(SHAW). I have a cable modem on 2nd floor of my house and a Linksys WRT54GL router. Now my brother living in the basement want to use his own Linksys WiFi router with this existing internet connection. Is there any way i can use both WiFi routers on same internet connection by using switch/router after DSL modem. Your suggestion will be much appreciated. Thank you.

my router has something called WDS. heres what the router says
Wireless Distribution System uses wireless media to communicate with other APs, like the Ethernet does. To do this, you must set these APs in the same channel and set MAC address of other APs which you want to communicate with in the table and then enable the WDS.

i had a netgear router that had a similar option but wasn't called WDS.