a router with QoS feature is one solution to control the download speed of your kid brother. i'm using an ASUS wireless router flashed with DD-WRT firmware. you can do lots like bandwidth shaping, packet prioritizing (you can prioritize P2P over YouTube), etc. if flashing firmware is beyond your forte, there are commercial routers flashed with DD-WRT such as Buffalo.btw, there's one feature you do. prioritizing ACK packets. it helps maintain your download speed even when you're uploading.