The Beginning
Summer Rockbell was a rambunctious, quaint girl who lived with her sister, Winry Rockbell, and grandmother, Pinako. She and her sister played every day with the neighboring boys Edward and Alphonse Elric, they lived with their mother.
Both sets of children had suffered their own losses and fought their own emotion filled battles, the girls lost their mother and father, who were doctors, in the Ishvalen War. Then boys' father had abandoned them and their mother, who patiently waited for his return until she fell ill and soon died. The grown-ups in their lives had left one way or another, leaving a sense of abandonment among them.
Just before Trisha Elric passed, Ed and Al had discovered their father's study with books upon books over alchemy. They took it upon their selves to learn alchemy, and Summer, who stuck to the boys far more then Winry ever did, sat alongside them learning alchemy.
When the day came that Edward decided to attempt human transmutation, Summer toiled away in the basement drawing up the massive and complicated circle needed. Once the boys came down the stairs with the ingredients, she was right there, gripping their hands and happy to help these two. And when the plans failed, she lost her right leg to Truth. When Ed grasped desperately to bring back his brother, she scrambled in step behind him to assist.
When the night was done, Al had carried both Ed and Summer back to the Rockbell's, covered in blood.