I am an only child.  I have no brothers or sisters.
Are you upset about that?
I suppose it is conceivably possible that i have a half sibling somewhere out there that i do not know about.
I think I actually do have one of those
If you look back at the entirety of human history, being an only child is rather uncommon.
I can see that
But with the cost of raising a child being what it is today, only children are becoming more commonplace.