On that aforementioned Reddit thread, one commenter observed that the nature of Chip and Dale’s relationship has “never really been stated. “
“A lot of people view them as brothers, including the guy who drew them,” that Reddit user added. “But it seems like only Walt [Disney] knew whether they were brothers or not, so it’s just kind of out there.”
That commenter is seemingly referring to Bill Justice, the animator who first drew Chip and Dale. Justice wrote in his autobiography the two characters are “simply little brothers,” but Disney has never acknowledged that familial relationship, according to the 2012 book Disney Trivia from the Vault by Dave Smith.