I think since the router only has a limited bandwidth your ping would be higher if there are more devices you have to share that bandwidth with, assuming they are all using the internet of course

yes

do people in your house use the microwave alot?

Unless the router/modem is right next to the microwave, it shouldn't affect it
Also get a router with QoS if you want to become the dictator of your internet

How would I fix this? are their routers with unlimited bandwidth?

This has not really been a problem until I got this new router from my ISP, its a dir 868l router.

please learn how to set up QoS

almost every internet related thread on this forum is because of people not using QoS

QoS not being properly set up will obviously cause ping spikes when other people are using the internet, but multiple people using the same wireless signal relatively close to each other can also cause connection issues occasionally

Does QoS affect the other people in the household by not giving them internet connection at all? Because my current router doesnt have QoS, so I guess I'll just switch back to my old router.

But I'd like to know how QoS works so I don't have even more problems.

https://en.wikipedia.org/wiki/Quality_of_service

http://www.pcworld.com/article/2689995/quality-of-service-explained-how-routers-with-strong-qos-make-better-home-networks.html

http://www.howtogeek.com/75660/the-beginners-guide-to-qos-on-your-router/

Basically you set a minimum bandwidth and if usage is too high, it bottlenecks the user so other users aren't affected.

a lot of routers also give you the ability to prioritize certain data over other data. specifically, I've set up mine to fully prioritize port 27015 from my IP over all other data in the house. Even if my brother is downloading a game at full speed, my ping in TF2 won't be affected at all (though mumble might be).

So in Netgear, would I just select TCP/UDP, just TCP or just UDP, for 27015?

and setting that to highest?