Nay, Congrats on the TTC decision.
I am an only child. I might've had everything I wanted and needed when I grew up, but I missed out on so much! My mom couldn't have more kids. I admired big families, they always seemed to have more fun. And now being an adult, I look back and know that having siblings teaches you valuable skills, like handling conflict. One thing I am not too good at. My DH is also an only child (brother passed away) and we don't have the huge family gatherings, we don't have brothers and sisters to go and visit. We both lost a parent, which means its only us and 1 parent left in this world. Should something happen to them, we'll be all alone! No one to remember our childhood with, laugh about family moments.
I had a great childhood, was loved by my mom and dad, but being older, I really do miss having a brother or sister.
For each it's a personal decision, and some don't have a choice, but to only be blessed with one child. But if you do have a choice carefully consider the pro's and cons and talk to people that are only children.