Why I have more than one child

So here's a conversation I had with Violet the other day.
Back story:
KT was at a friends house, and she and Violet had been not getting along anyway.
But apparently arguing with your sibling is a pasttime at Casa de 'R' and when there isn't anyone to argue with, boss around and boss back meloncholy sets in.

Violet: I'm Bored, I wish KT was here to play with.
Me: It's not KT's job to entertain you.
Violet: Yes it is, that's why we got her!!!
Me: ROFL!! (litterally)
Violet: Why are you lauging?
(puzzled look on her face)
Me: ROFLLLLLLL (and she still has no idea why I am laughing) more ROFL
Violet: What is so funny?
Me: (through tears of laughter) ...I couldn't explain it to you so you would understand how funny it is to me. (but I know my friends are going to bust a gut over this!!!!)