This is how The Legend of two Cybertronian brothers goes in Friendship is Magic.
[We see a book which opens revealing the words "Once upon a time..."]
Narrator: Once upon a time, on the magical planet of Cybertron, there were two Cybertronian brothers who ruled together and created harmony for all the land. To do this, the youngest worked in the Iacon Hall of Records as a librarian. And the elder trained as a gladiator in Kaon. Thus, the two brothers maintained balance for the planet and its inhabitants: all the different kinds of Transformers. But as time went on, the elder brother became resentful. The Transformers relished and admired the work his younger brother brought forth, but shunned and pushed away his gladiator skills. One fateful day, the elder brother refused to stay a gladiator. The younger brother tried to reason with him, but the bitterness in the elder one's spark had transformed him into an evil Cybertronian warlord: Megatron. He vowed that he would bring war and destruction to the Transformer planet. Reluctantly, the younger brother harnessed the most powerful relic known to the planet, the Matrix of Leadership. Using the power of the Matrix of Leadership, he defeated his elder brother and banished him permanetly in one of the Cybertronian moons. The younger brother became Optimus Prime and took on responsibility for both being leader of the Autobots and student of Alpha Trion and harmony has been maintained on Cybertron for generations since.
[We see a unicorn named Twilight Sparkle reading the book]
Twilight Sparkle: Hmmm. Matrix of Leadership. I think I've heard of that somewhere before. But where?