- "My name was Mary Alice Brandon. I had a little sister named Cynthia. Her daughter - my niece - is still alive in Biloxi."
Cynthia Brandon was the younger sister of Alice Cullen, when she was still known as "Mary Alice Brandon".
Cynthia was nine years younger than Alice. Despite the age difference, however, Cynthia and Alice were very close. Her father was a jeweler whose work kept him away from home for days at a time, so their mother took care of Alice and Cynthia. Her father remarried within six months after the passing of her mother, and her stepmother treated her like a favorite while treating Alice very coldly. For this reason, she remained in the dark about her sister's discoveries of the mystery behind their mother's death. After Alice was locked up in a mental asylum and became a vampire, Cynthia married and had a daughter.
She had since passed away, but her daughter is still alive in Biloxi.
Cynthia is only mentioned in New Moon when Alice visits Bella; and tells her of her discoveries about her mysterious human life, and found out that she had a sister, who had since passed away, leaving a daughter who still lives in Biloxi. It's unknown whether Cynthia knew that Alice was confined to the asylum.