Some years after the humans were made, a few select people were chosen to each hold a unique power. These powers were split into a few categories. There are the Kings, The Flames, The Caretakers and The Order. Let me explain what each of these categories did.
The Kings – They were ordinary people with an extraordinary ruling mind. They were the popular ones in school, he CEOs of major companies, the presidents and kings of countries. They were made to be in positions of authority. This is the largest group out of the 4 categories afore mentioned.
The Flames – These people had flame attributes within them and could use various powerful weapons, as we already know. Within this category are 3 other main branches:
The Flames of the sky e.g. Vongola family, Millifiore family, etc
The Flames of the earth e.g. Shimon family
The Flames of the elements
The Caretakers – These were normal people who did not have any special power. The only thing that they could do was to accept, support, love and care for those who belonged in the categories Kings, Flames and Order. Examples would be Sawada Nana, Sasagawa Kyoko and Miura Haru.
The Order – They would watch over and make sure that the use of all types of powers was appropriate and would also punish those who did not use it according to their rules. Those who belonged to this group were Vindice and Arcobareno.
For those born of the Flames, we know of the story of those of the sky and those of the earth but the story of those of the elements was kept hidden from generation to generation; until a certain man by the name of Giotto fell in love with a young lady (name withheld) who had the flame of the elements. As Giotto started the vigilant group Vongola, the young lady started a training centre for young children who had the flame of the elements so that they could control it. This training centre was called The Neutral.
Since the day of its founding, it was decided that this centre would not be directly involved with Vongola unless the situation calls for it. Due to this decision, no one in the Vongola knew of its existence until a pair of twins was born into the Sawada family. These twins grew up loving each other like no other brother and sister did. However, around the time when Vongola ninth visited the Sawada household, he noticed that the little girl also had an unknown but powerful flame besides the sky flame. Not knowing what to do, he just left her alone and sealed the boy's power. The next day, this little girl found her brother being bullied and jumped in to save him. While doing so, she accidentally scared them away with her unknown flame.
She thought it was a harmless accident, until later that evening, 3 grown men took her away from her family. They gave an excuse to the mother and told the father it had to do with Vongola and they left with their only girl. She was never seen again until shortly after Reborn had promised to form the boy into Neo Vongola Primo. The names of the twins are Sawada Tsunayoshi and Sawada Yuki. This is their story.