Masonic Lodge in Turin. Here he knew the Italian socialist and freemason Giovanni Lerda (1853-1927), a close collaborator of Cesare Lombroso.

In 1887, Peano married Carola Crosio, the daughter of the Turin-based painter Luigi Crosio, known for painting the Refugium Peccatorum Madonna. In 1886, he began teaching concurrently at the Royal Military Academy,