If QoS is applied to the entire router, as in not just connections distributed through the wireless but the wired connections too (which is most likely in my view), then it will also apply to ethernet connections directly attached to the router. However latency is reduced via direct connections, as for how much, it probably won't make a considerable impact.

Essentially if you're having problems you should talk to your mums partner and see if he'll compromise with you. I'm not sure exactly what he's implementing QoS for but I doubt it's very important, and these days it doesn't really do much apart from cause annoyance anyway. If he won't consider turning it off, maybe he'll consider adding your IP / Steam's protocol as a higher-service rule. Or maybe there is a way to exempt it from QoS, I'm not too sure about that.

-------
and victorious in war shall be made glorious in peace.

---

Well generally Internet is faster the less users are on the router because the load is lower. However latency is clearly an issue if QoS is applied to the packets, and though reducing the users tries to counter this problem, it won't do that much.

If QoS is applied to the entire router, as in not just connections distributed through the wireless but the wired connections too (which is most likely in my view), then it will also apply to ethernet connections directly attached to the router. However latency is reduced via direct connections, as for how much, it probably won't make a considerable impact.

Essentially if you're having problems you should talk to your mums partner and see if he'll compromise with you. I'm not sure exactly what he's implementing QoS for but I doubt it's very important, and these days it doesn't really do much apart from cause annoyance anyway. If he won't consider turning it off, maybe he'll consider adding your IP / Steam's protocol as a higher-service rule. Or maybe there is a way to exempt it from QoS, I'm not too sure about that.

---