The Third Sibling of the White-Faced Women was a sibling of the two white-faced women who were associates of Count Olaf. She was killed in a fire that the white-faced women suspected was not a coincidence. It is possible this fire was set by either Olaf or another arsonist who was an associate of Olaf.
In the TV series, they clarify their sibling was female, while in the books, their gender is ambiguous.
- The Slippery Slope (Mentioned only)