Susan Foreman's mother

Susan Foreman's mother was the wife of a Cardinal on Gallifrey. On the day that she was giving birth, Lord President Rassilon sent a number of guards to terminate the pregnancy due to it violating the Legacy of Rassilon; this proclaimed the only the Loom Born could inherit the legacy of Rassilon. The First Doctor travelled to the past and saved Susan and Patience. (PROSE: Cold Fusion) Susan was apparently the last child born after the Pythia's Curse, her mother died during childbirth. (PROSE: Lungbarrow)

Upon seeing a picture of Susan Foreman, the hermit said she took after her mother. (PROSE: The Three Paths)

Parallel universe
In another universe, Susan was the daughter of the Doctor's daughter. (AUDIO: Auld Mortality)