I am one of the few people among my friends who is an only child.  
SO thankful I am an only child with no siblings
I wonder what percentage of people are only children
Not sure but the term applies to people who have never had any siblings at all
I am aware.  I wonder if that means step brothers and sisters too
You can have step siblings or half siblings but still be an only child
So half siblings aren't considered real family?
Correct and throughout history only children are rare
I am sure that back then they wanted to reproduce as much as possible
In the US the only time the percentage of families with only child increaseed was during the great depression