So here is my theory on Mohatu's reign, enjoy! :3
After Mwanga and Zuberi became the rulers of Pride Rock, a certain lioness showed up in the lands. It was Nuru, the queen's sister. She was looking for a mate, and wanted to come to the Pridelands for the rest of her search. At first, Zuberi was very hostile towards Nuru, but later on, he began to realize he was in love with her. He proposed to her on the last day of her stay. She accepted the offer. However, Mwanga grew angry at her sister for stealing her love, but later, Nuru admitted that Mwanga should be queen, and left the pride. About 6 months later, she gave birth to her and Zuberi's child, a little boy. She named the cub 'Mohatu'.
Once Zuberi found out about how Nuru had left, he went on a search for her. Finally, he found her, and told her that he loved her, and did not want to lose her, or their child. He then began to realize that he and Mwanga still didn't have a cub, and that Mohatu could be the next king. She was accepted into the pride once again. However, soon after her welcome, Mwanga gave birth to Zuberi's cub, another little boy, whom she named 'Choyo'.
Nuru was forced into raising her child in the Pridelands by the king, who had grown dark and insane over time. Eventually, a lion named Kosa defeated the king, saving those who were punished over his cruel rule. However, the rogue only stayed ruler for a short period of time, and eventually left the pride.
Meanwhile, Nuru and Mwanga had difficulty deciding who would be future king. They would constantly argue, and eventually, the two got in a huge fight, which ended with the death of Mwanga. Ashamed of herself, Nuru ran far away, deciding that she was a murderer.
The two cubs were put into the paws of a young lioness, named Azalia. She raised the cubs as her own, and eventually took the role as queen of the pride. In the meantime, Choyo and Mohatu grew well, as they were now young teens. Azalia decided that Mohatu would be the future king. However, Choyo grew angry with his mother's decision. However, he kept his anger a secret, at least for now.
When they were young cubs, they met two sisters, Asali and Thema, who later became their mates. Asali married Mohatu, and they had three female cubs, the oldest named Uru, who would be future queen. Choyo and Thema had Ahadi and Bahira. In a attempt to take the throne as his own, Choyo tried making a deal with his half brother. He would let Mohatu chose one of his sons as a mate for Uru. However, Mohatu decided that it would be best to let Uru decide who she wants to marry.
Angry, Choyo lunged at Mohatu. The two broke out in battle, and it ended only with the exile of Choyo, Thema, their cubs, and their followers.
Eventually, Choyo died of old age, and the rogues were forced to find a pride. Thema, now insane, found the Outlands, a once beautiful place, but now it was a wasteland. Thema swore revenge on Mohatu, and she would continue to plot.
Meanwhile, Mohatu became worried with the fact that Uru might not find a mate, and continued to think of the possibilities that she could marry a handsome male...
..or her own half cousin?
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Yeah, I was in a rush when I typed this.