what if Mufasa and Scar had different mothers, but the same father? And that they were born at the same time? And because of this, their father had no different choice as to make the fight as young adults to decide who would be the next king? Then Mufasa beat him leaving Scar whit a uhm scar on his eye.
Scar was on the range from leaving the pride after that incident, but decided to stay hoping that he was the one to become king one day. And Mufasa would let him stay because he felt obligated to do so, although he wasn't too found of it.
I just thought it out while browsing to some old fanart lying around^^
I just kind of think that there might be a possibility for this to work as a theory, and I'd like to hear your opinions on this