Here are the extra siblings as adults

Akilah and Jali are the younger brother and sister of the revered Mufasa and despised Scar, born only a few minutes after their more infamous brothers. Because of certain life events and the encompassing nature surrounding the story of the wise and virtuous king betrayed by his own brother/Head Guard, Akilah and Jali are rather obscured from history as time goes on.

They were often taunted as cubs for just being spare pawns in case their more promising brothers ever failed or something happened to them. Their existence was almost a joke, as the Pridelands had never before seen a royal couple bare more than two cubs in a litter. What cruel fun it had to be by the Great Kings to have them be minutes from being in line to be the next Ruler or Fiercest Warrior, and instead to be cast in the shadow of Mufasa and Askari.

Luckily, thanks to Uru's determination to keep her kids united, these jabs were never really what would cause problems between the four siblings. Akilah was the peacemaker who got along with the others, but always at the cost of his own mental health, and Jali's difficulty to show her true feelings could cause a rift between her and Askari, who was more emotional and snide and easily offended. Mufasa and her are a bit closer, though a certain incident will divide the four in a tragic way once things in the family become tense.

Also one of these two do die tragically, though it is sort of unrelated to the previously mentioned incident.

Design wise, i wanted to keep Akilah as the halfway point between his big brothers, to symbolize his mediator role in their sibling dynamic. And like i mentioned in their update, Jali is to stand out more from her brothers in more ways than one. She takes after her paternal grandfather Mohatu in looks while also sporting the mane mutation that shows up in her mother Uru, and Uru's mother Shujaa, as well as being the most like Ahadi personality wise than any of her brothers.
And as always, the two's eye color is purposefully not meant to be the same as Scar's, they are two different shades of green, from different sides of the family.