Kys is also short for "know your siblings", or even "keep yourself safe".
person1: "how did you not realise that your brother overslept? You should kys!" (example 1)
person1: "I'm not feeling very well."
person2: "Awh, that sucks. Kys!"
When some one makes me mad I'll be like kys which means kill yourself
Lilly- "I'm soooo hot"
Me- Kys hoe
-kys in sports games or fps games often used in short for "keep your score" when worse players try to complain about your own gameplay.
"you're terrible you only have 3 kills"
"You have none dude how about you kys before you worry about mine"
Kys the insult of kill yourself
Guy1 yo I shaged ur nan bruv. Guy2 wtf kys.