Sandalpho
Oswald the Lucky Rabbit and Mickey Mouse were among the first creations of Walt Disney. Although Oswald was the earlier of his many creations, Mickey ends up becoming the iconic face of the Disney company and theme parks. Oswald was nearly forgotten and has only appeared with Mickey in a small number of Disney medias, that mostly focus on classic Mickey. Due to Oswald not being given a modern updated look, like Mickey has. That is why Oswald is mostly featured as a cameo now a days, rather than be treated as one of Disney's central characters.
Although Mickey is the face of Disney, fans still like to include Oswald, who is viewed as Mickey's older brother from being created before him. Mickey being a mouse and Oswald being a rabbit, however, does have a few people questioning that family view. With mice and rabbits being separate species, even though there is a resemblance energy between them. Of course, Mickey Mouse and Friends has some history of interspecies relations, so the idea that the pair have mixed Mouse-Rabbit heritage is not implausible. The fact that Mickey's parents have rarely if ever been depicted further opens up this possibility.
Many fans of the modern Mickey cartoon were upset that Oswald did not play a bigger role, believing that he deserved to be at least a recurring character instead of just being a cameo. That is why they prefer the Epic Mickey series, with the second game having the brothers team up