1. Simba might have been Scar's kid.
Dude lions are ejected from their natal prides around three and wander the wastes as nomads, either alone or with their brothers. Until one fateful day they think, "This is bullshit," and usurp a neighboring pride with a weak male. Coalitions tend to have larger territories and more kids because they can split procreation and patrol duty and sorry there's no lion Maury so we're just taking Sarabi's word for it.
2. Mufasa was only king of his own deluded mind.
3. Scar was getting all the sexy times.
4. Mufasa was a lying liar that lies.
5. Murder is an occupational hazard, whatever.
6. There's no such thing as a bloodless coup.
7. Simba and Nala are siblings.
8. To recap, this is his sister. Or cousin. Or both.
If you just tried to justify this, you can never judge Jaime and Cersei Lannister again.
9. This is Simba's true fate.
10. Bonus! Rafiki is an abomination against nature.
Though called a baboon (left) and have the coloring and tail to go with it, that is clearly a Mandrill (right) face. What the hell is going on here? Did some scientist recreate Face-Off to make a super-intelligent, artistic monkey hybrid and then unleash it onto the unsuspecting lion populace to trick them into ritualistic inbreeding? Face it, that's the only logical explanation.
Lion facts courtesy of Feline Conservation, BBC, and Wikipedia.