The background to Walton's character is established in his early letters, in which he describes to his sister, Margaret, his feelings that he was set upon earth to "accomplish some great purpose," and that "success shall crown [his] endeavours," despite his flagging spirits. This foreshadows what the reader will later learn about Victor, himself, and establishes a similarity between their characters.
When Walton's crew finds Victor, Walton's initial response is surprise that a man so emaciated and apparently close to death should first inquire as to "whither you are bound." He is interested further when the stranger appears satisfied with the answer that the crew is bound on a voyage of discovery.
Victor's initial silence worries Walton, but he swiftly becomes impressed by the "interesting creature" he has picked up and becomes protective of him, restraining his own curiosity and that of his men, who would all like to interrogate him about his purpose in the ice. Very swiftly, Walton forms an intense attachment to Victor, whose gentle manner and "deep grief" draws out Walton's compassion until he "begin[s] to love him like a brother." This is before Walton even knows Victor's story, but he is extremely moved by the broken spirit he perceives in Victor——perhaps conscious that he, too, can imagine his own spirit becoming broken as a result of his endeavors——and sees in him a potential "brother of my heart."