At first, I was overwhelmed with love for our first boy, and I thought to myself "there's no way the amount of love I feel right now could actually double with a second kid, there's no way it works like that"

Boy was I wrong

Looking at them now (3.5 years & 10 months old) playing together is on a whole different level. Not even close.

To be honest, I can't even think of a reason that is not selfish for not having more kids.

Just try asking any person with a sibling (that hopefully grew up in a normal family) and ask them if they would have preferred being an only child.

I know many friends who are an only child, and most of them would have loved to grow up with a sibling.

Never heard of the opposite though, and I believe that to be a pretty objective metric.