Talk:Sweetie Belle/@comment-26973802-20140321195645/@comment-26973802-20140323221023

People were speculating it under the episode's page due to the similar scenario of feeling overshadowed by an older sister

As for King Sombra there was no confirmation that's just my headcanon, and it makes sense: Luna feels jealous but won't try to overthrow Celestia, and before they banish King Sombra, either during a fight or an exchange of words, Sombra senses Luna's resentment so he casts a curse to magnify it (without her knowledge), which, like his curse on the Crystal Empire, survived his banishment, and the curse was gradual assuming Sombra was before Discord