This feels like a really stupid question but I genuinely don't know. Gliders existed before powered airplanes, right? So people would probably could have made paper airplanes for fun prior to the Wright Brothers, but I have no idea and just had this as a weird shower thought and was curious about it now.
As a matter of fact they totally did. Even kids. It's been a well known lil trick for at least hundreds of years, probably longer.