Helen Swan was the Wife of Geoffrey Swan, the mother of Charlie Swan, the grandmother of Bella, grandmother-in-law of Edward Cullen, and great-grandmother of Renesmee Cullen. She never appeared in the series but she was mentioned at Bella's Wedding.
Biography
History
It's mentioned in The Twilight Saga: The Official Illustrated Guide that she and her husband, Geoffrey did not think they could have children, so Charlie was an unexpected but welcome surprise. He was born when Helen and Geoffrey were in their mid-40's.
By the time their son reached adulthood, Helen developed early stages of Alzheimer's disease and Geoffrey's mobility was curtailed by severe arthritis, which kept Charlie from going to College.
After Charlie married Renee and had Bella, their conditions worsened. When Renee left with Bella, Charlie remained in Forks to take care of his parents, though he really wanted to follow them.
In 1991, within six months of each other, Geoffrey and Helen passed away, leaving Charlie alone.
Breaking Dawn
"They were your Grandma Swan's... We had a jweler replace the paste stones with sapphires."
At the beginning of Breaking Dawn, Bella inherited two hair combs in silver, which used to belong to Helen as Wedding presents from her parents and her "Something old and something blue," though the combs' pastestones were replaced with sapphires.
In the movie, there was only one comb.
Life and Death: Twilight Reimagined
In Life and Death: Twilight Reimagined, Helen's grandson, Beau Swan became a Vampire and faked his death. A funeral was held and his casket was buried next to Helen and Geoffrey's.