Growing up, we always assumed that Scar and Mufasa were brothers, and therefore, Scar was Simba's uncle. It's not something we ever questioned.
But it's turns out we had the links between The Lion King characters all wrong. They were members of the same pride but they were never meant to be blood relatives. According to Rob Minkoff, the film's director, and Don Hahn, the producer, the relationship between the characters was based on the real family bonds between lions living in the wild.
Hahn explained to Hello Giggles "We talked about the fact that it was very likely they would not have both the same parents. The way lions operate in the wild... when the male lion gets old; another rogue lion comes and kills the head of the pride."
He also added "Occasionally there are prides that do have two male lions, in an interesting dynamic because they’re not equals. One lion will always kind of be off in the shadows. We were trying to use those animal truths to underpin the story of we sort of figured Scar and Mufasa can't really be from the same gene pool".
Now that we really think about it, it makes sense. In fact, the thought put into every aspect of The Lion King makes us appreciate the film even more.