I'm what they call an only child. Someone who has no brothers or sisters.
Do you know what percent of children are only children?
Well around the 20th century is about the time birthrates started dropping drastically in life. Maybe due to women joining the workforce more?
I believe many more people want to live their lives without children nowadays.  It was frowned upon in a way not to have children long ago.
It happened in the past during The Great Depression as well. There were more only children in those times.