"Tracing back Tchaikovsky’s pedigree, we do not find a single name connected with music. There is not one instance of a professional musician, and only three can be considered amateurs— his mother’s brother, Michael Assier; her sister Catharine, in her day a well-known amateur in Petersburg society; and the composer’s mother herself, who sang the fashionable ballads of her youth with feeling and expression. all the rest of the family— Assiers and Tchaikovskys alive— not only lacked musical talent, but were indifferent to the art. Thus it is almost impossible to ascertain from whom Peter Illich inherited his genius, if indeed there can be any question of heredity. His one certain inheritance seems to have been an abnormally neurotic tendency, which probably came to him through his grandfather Assier, who suffered from epilepsy. If it is true, as a modern scientist asserts, that “genius” is merely an abnormal physical condition, then it is possible that Tchaikovsky may have inherited his musical gift, at the same time as his “nerves,” from the Assier family."
▼ The Life and Letters of Peter Illich Tchaikovsky (1905)
, by Modeste Tchaikovsky,
edited from the Russian by Rosa Newmarch (via sufferforyourmusic