Oh lord, do I have an answer.
I was an only child for a while. It was lonely. Always wanted a sibling and apparently asked my mother on multiple occasions to buy me one off the black market. True story. Once I turned 13, Mom was pregnant with twin girls by a man whom she had just married, and he himself had one girl and twin boys already. Yeah, that's right. I wished for A sibling and got 5. Plus an older cousin that moved in with us.
Nonstop energy and loudness and craziness in our house. I could never being friends over in highschool because the house is in constant disarray and there's kids and toys all over. It was a rough adjustment... I'm happier with siblings but when it comes to being careful what you wish for, I suggest you invest in a hardhat and some therapy if you start asking.