I thought that there was an older brother in the show.

Ritchie's older brother, Chuck, was only around for season 1 and then he was never heard from or mentioned again.

Alien abduction?
Group hallucination?

You decide. :-)

Ritchie's older brother, Chuck, was only around for season 1
... and 2.

Ritchie's older brother, Chuck, was only around for season 1 and then he was never heard from or mentioned again.

Alien abduction?
Group hallucination?

You decide. :-)

In the final episode when Howard made a toast after Joanie and Chachi's wedding and thanked the viewing audience for being a part of their family, he didn't refer to Chuck. It seemed that after the first season, Chuck wasn't needed when Fonzie became the main emphasis.

It didn't take long for the producers to realize that Fonzie had a big brother/mentor type relationship with Ritchie. Because of that the character of Chuck was no longer necessary and he simply ceased to exist in the Happy days universe.