I don't really get Sebastian and Ciel's relationship. Someone help?

Well, according to most ppl, their relationship is just a typical master-servant relationship since 黒執事 is a shonen manga/anime. But sometimes in the マンガ and the anime, there are scenes that look like they are having a romantic relationship, even the 作者 of the マンガ 発言しました that intially the マンガ was supposed to be a やおい manga, but her idea was rejected and she was forced to change the マンガ into how it was now. So, the answer is quite ambiguous.