People who awakened during childhood went through a lot of stuff. Familiarizing oneself with the changes in the body and mind and understanding one's new roles in society was more bearable when one was older.
The earliest hurdle they had to face was the body transformation. The forming of a mana core in an esper body and the corrosion vessel inside a guide was not an easy process. The stress it brought to a child's body was even harder. In this regard, the twins were rather lucky.
Not because they did not experience it. They did--they were unconscious for three days, not including the night they collapsed. But they were lucky that they immediately fell unconscious from the exhaustion of using mana for the first time.
