You can choose your friends, but not your family...
I'm guessing that your brother bought another computer, so it's time to hit him up for a favor. You need to figure out which motherboard is in your machine, then hit the manufacturer's site for drivers. Then download them, and burn them to a CD. The internet won't work until you install the "LAN" driver. (Local Area Network). try and find the "chipset identification utility", and install that first. (This if it's an Intel chipset).