Pi feels intense guilt about Ravi. When Pi leaves to investigate the explosion on the ship, he shakes Ravi but decides to let him sleep. Big mistake. Ravi goes down with the ship.
Pi still feels guilt over this later, when the blind Frenchman (who is in some ways a double for Pi, and a product of Pi's madness) admits to killing his brother. There's also a reference to Cain (yeah, the Cain that killed his brother Abel in the Bible) in Part 2, Chapter 61 after Pi clubs a fish to death.
Perhaps Pi feels such intense guilt over Ravi because Ravi has such a lively and lighthearted spirit. He's irreverent. While Pi worships Mamaji, Ravi calls him a "fish face" and points out how enormous Mamaji's chest is compared to his legs. When Pi earnestly tries to understand both Islam and Christianity, Ravi jokes that Pi is only attempting to fill the week with holidays:
"At the rate you're going, if you go to temple on Thursday, mosque on Friday, synagogue on Saturday and church on Sunday, you only need to convert to three more religions to be on holiday for the rest of your life." (1.24.2)
If Ravi were in your English class, he'd throw paper airplanes. He counters Pi's seriousness with a playfulness which, perhaps, teaches Pi as much as Mamaji or one of the Mr. Kumars. In terms of competing worldviews in Life of Pi, Ravi represents lightness of spirit, ease, and joy.