To be honest I think that Wolfrang Amadeus started his composer caareer because his father Leopold was a musician too and recognized his talent. Also his sister Nannerl was a talented musician too, even if not like him. Also Johann Sebastian, his father Johann Ambrosius was a composer too, and his grandfather Christoph too. Not to mention Johann sr, Johann Jr and Eduard…
“Nepo babies” happened a long ime ago. Honestly living in a musician family helps a lot for havin already musical instruments and parents that could recognize talent. I know two musicians that have perfect pitch and both of them have parents that are playing music and noted early their kid could easily recognize notes.