From Wikipedia: "People Associated with Anne Frank" -

Eva Geiringer shared a remarkably similar history with Anne. The Geiringers lived on the opposite side of Merwedeplein, the square where the Frank's apartment was located, and Eva and Anne were almost exactly the same age. Eva was also a close friend of Sanne Ledermann, and she knew both Anne and Margot.

Eva described herself as an out-and-out tomboy, and hence she was in awe of Anne's fashion sense and worldliness, but she was somewhat puzzled by Anne's fascination with boys. "I had a brother, so boys were no big thing to me" Eva wrote. But Anne had introduced Eva to her father when the Geiringers first came to Amsterdam "so you can speak German with someone" as Anne had said, and Eva never forgot Otto's kindness to her. Though they did know each other on a first-name basis, Eva and Anne were not especially close, as they had different groups of friends aside from their mutual close friendship with Sanne Ledermann.

Eva's brother Heinz was called up for deportation to labor camp on the same day as Margot Frank, and the Geiringers went into hiding at the same time the Franks did, though the Geiringer family split into two groups to do so - Eva and her mother, and Heinz and his father. Though hiding in two separate locations, all four of the Geiringers were betrayed on the same day, about three months before the Frank family.

Eva survived Auschwitz, and when the Russians liberated Birkenau, the women's sector of the camp, she walked the mile-and-a-half distance to the men's camp to look for her father and brother, finding out much later that they had not survived the prisoner march out of Auschwitz. But when she entered the sick barracks of the men's camp, she recognized Otto Frank, and had a warm reunion with him.

Eight years later, Otto married Eva's widowed mother Fritzi, thereby making Eva a stepsister of Anne. Eva later wrote her autobiography Eva's Story: A Survivor's Tale by the Stepsister of Anne Frank,[1] which served as the inspiration for the development of a popular multimedia stage presentation about the Holocaust called And Then They Came for Me.