When Bugs finds Bud outside the library, the two make plans. Why does Bud think of Bugs as his brother?

Bugs gets his name from the time when a cockroach crawled into his ear. He suggests he and Bud go west to find opportunities, but when Bugs makes it onto the train setting off from the Hooverville, Bud does not. I think Bud views Bugs as having similar traits to himself.