When Sebastian Michaelis was still known by other names (Though quite often Sebastian was his first name-it suited him), roughly seven years before he was contracted by Ciel Phantomhive, he met an Egyptian demon commonly known as Lady Felisa. The pair worked together on several occasions, as demon summoners with a good deal of knowledge on the subject were able to surmise that they worked extremely well together-both were intelligent, and elegant. Both preferred using sophisticated and quiet ways of carrying out work, though Felisa was stealthier than Sebastian, and Sebastian was physically stronger, and better at brawling. They were agreed to split their masters soul, and when they were free once more, they remained by each others side, finding it easier than departing.
Sebastian had always loved cats, and Felisa was indeed a cat demon.
In turn, Felisa was eternally amused by Sebastian's humorous ways of intimidating enemies-especially when, shortly after, she caused him to blush and fall head over heels for a fluffy kitten.
So, eventually, an event quite rare occured: Demon spawn. Yes, sadly that term sounds like they're tadpoles or insect babies, but the reality is surprisingly human.
As is always done, neither of the boys were named, after all they would be named by their masters in the future.
However, both of the boys were dissapointments, to their father. The elder, who would grow up to be Sebastian Cortez, was flamboyant, and held no hatred of humans, or lust for their souls. The other, who would be Simon one day, was rather indifferent and reserved about it all, and showed no inherent talent for demonic abilities. It was obvious from the start that Simon was a cat demon like his mother, but Sebastian Jr. was more difficult to identify. Eventually they reached the conclusion that he was canine in origin, and neither of the parents knew where that came from. Sadly, Sebastian had to leave when the children were still young, to respond to a summoning. Felisa was left with the children alone, and could not eat souls, trapped as she was with her progeny.

But. Well, Sebastian had not been completely honest with Felisa. The summoning he had to respond to was not a summoning at all. After all, his children were a disappointment. But there was a child, a young boy in London, whom he had watched. Watched him become an orphan, be kidnapped, and abused in all ways imaginable. And his soul...instead of growing weaker from the hardships he'd been dealt, it resonated more clearly and stronger than any he had ever seen before. It was driven by  pure hatred, vengeance, and determination. It was not good. Not evil. It was just revenge. And so he watched, until Ciel Phantomhive would have died, and then he initiated the summoning himself. He never enjoyed just taking souls without contract; the soul was forever marred by that. If it were willing ,well, then it was all the more appealing.
So he ascended to Earth, and while the boy was surrounded by the cultists who had so wronged him, he approached the youthful earl, and suggested that a Faustian Contract would be helpful. He did not lie, or make it seem a better deal than it was. In fact, he pushed the cons as much as he could, to test the boy's will and courage. And, at the end of it all, he accepted. He accepted the contract without so much as a waver.
That, Sebastian thought, was what a true demon son should be like.

So Sebastian left, to become Michaelis, and everyday his hunger for his new masters soul grew. He began to forget about his children, such disappointments they'd been. Felisa, though....he did miss her, but his contract came first, as always. Every night, though, he would call upon her image, something he had kept a secret, even from Ciel. They would talk in the night, but as time went on, more and more, she would not appear, or if so, only to tell him the children needed her. And he would scowl, and stand at the window, waiting for the morrow impatiently, when he could work to take his mind off his missing love.
Overall, though, he was satisfied, doing what he did best, serving a master, and, for once, an intelligent, young, purely driven master. The perfect soul, in his opinion.

A year passed, as everything in Black Butler happened. Or at least, season one. I may write a summary of that, but I didn't write it, so it would be rather boring. Watch it, if you really must know.

Wowwww...didn't expect that XD.

Haha XD.

Holy cow- shocking. Riveting, even. XD It's three AM, I felt like using big words, and I'm officially re-addicted to Meet the Robinsons. What else is new?

But seriously, to quote a famous panda- "That was severely cool."

...ily <3