Sergei Rachmaninoff and his mentor, Pyotr Tchaikovsky, share a penchant for melody. However, the similarities don't stop there.
#1 Not Destined for Composition, Were They
Tchaikovsky's parents intended that Pyotr study law and work in civil service. He shocked them by becoming a composer instead. Granted, Tchaikovsky's ultimate earning potential in civil service vs. music probably wasn't terribly different!
It was always obvious that Rachmaninoff would be a musician. However, nobody thought he would, or even should, be a composer. Such sentiment included his own teacher Nikolai Zverev, who discouraged him from composition and they eventually stopped speaking as a result. Clearly, his teachers and critics grossly underestimated modern audiences' obsession with virtuosity.
#2 Childhood Trauma
Tchaikovsky was sent to a boarding school at the young age of ten. Already troubled by the separation from his parents, his mother died when he was just fourteen.
Rachmaninoff's parents were wealthy but his dad squandered the inheritance through various ill-reputed pursuits, causing his parents to divorce when he was ten.
Both composers deeply struggled with depression. Tchaikovsky's was due in large part to being gay in a time and place that couldn't deal with it.Rachmaninoff's came from his desire to be a composer. Even though he was a famous pianist, Rachmaninoff faced considerable criticism for his compositions. The premiere of Rachmaninoff's Symphony No. 1 was terrible with typical criticism such as this from César Cui:
"If there were a conservatory in Hell, if one of its talented students were instructed to write a program symphony on 'The Seven Plagues of Egypt,' and if he were to compose a symphony like Mr. Rachmaninoff's, then he would have fulfilled his task brilliantly and would bring delight to the inhabitants of Hell."César Cui
Rachmaninoff didn't compose a single note for three years. Following much psychotherapy, Rachmaninoff got over his depression-induced writer's block enough to compose the Second Piano Concerto in 1900.