Kay was Slak's baby brother. Slak was making sleepover with lil of his friends (2 friends- Vie n J). His mom and your mum was close friends so his mum invited you on his sleepover (even if you ware enemies).

When you go to his house you see him playing with his lil brother (Kay)...

"Who are you?" Klay say "Just a ... Nobody." Slak say "Why are you here?"