Avenarius was the second son of the German publisher Eduard Avenarius and Cäcilie née Geyer, a daughter of the actor and painter
Ludwig Geyer and a (step-)sister of
Richard Wagner. However, there is speculation that her father was the biological father of Richard Wagner too. Richard Avenarius's brother,
Ferdinand Avenarius, led the cultural organization
Dürerbund and belonged to the initiators of a culture reform movement in Germany. Wagner was Avenarius's
godfather. ==Bibliography==