Ghosth, your consumer grade router will easily get flooded by an external fast network able to stream video at a high rate of speed to a computer on your network.
It probably doesn't matter what router you have - you mention DSL, which probably means in the neighborhood of 1.5 to 3 Mb/sec down and 128 to 512 up which means even a router from the turn of the century even should have little problem keeping up. So unless you have some sort of DSL I've not heard of, it's your connection that's getting saturated, not the router.
If either whatever is on the other end is sending enough data to saturate your connection - or his system is sending enough data to saturate your connection up - then you'll experience exactly what you described. I once called an ISP to report that a T1 based connection had gone down - only to find that someone in marketing had decided to send a mailing of epic proportions to 75 to 100 recipients. I literally couldn't get a ping to anywhere through the connection. I realized what happened when the T/S rep called back and said "No, the line is fine - but what I see is near 100 % utilization, and it's all SMTP traffic".
Unless you can pull the plug on him, then you are going to need a router that lets you throttle bandwidth. If you do change routers, don't get the FVS318G (even though it does support throttling) - I can say from personal experience that it does some "odd" things with streaming traffic that I could only resolve by getting an different brand. In my experience though, the bandwidth throttling doesn't always work as well as you'd expect, so you might still have problems.
Personally, I think the best throttling is the threat of - as in "You mess up my sim again, and my hands will be around your neck..."
But sometimes families are too complicated for the simple solution.
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