How to limit download speed?

I do not know a lot about computers so here goes.

Situation: I have two computers, one in my room, one in the living room. My parents are constantly on youtube therefore making me lag enough where my latency in online games are too spiky. I don't know much about my internet connection speed except I'm using DSL and I can download at a max rate of 200kbps and my ping/latency is generally solid in games. My guess is when my parents are watching videos on youtube, it downloads at 200kbps making me extremely slow. Is there anyway to cut the download speed of that computer to around 100-150kbps? They're my parents so I don't mind them using it as long as it doesn't lag me like crazy. 100kbps is fast enough for them to stream videos on youtube, does anyone know how I can do this if there is a way? And will their downloading at 2x slower mean better latency for me? Thanks

you have to get the ISP for your router from the manufacturers website
type the ISP into your web browser
it will pull up the router menu
you can set bandwidth limits on certain ports and/or set a port as high priority

edit-some routers have to be plug directly into the computer to do this
so plug your Ethernet cord into the Ethernet port on your router and straight into the back of your computer after you get your routers ISP of course