Catherine O'Hara is not a twin. She is the fifth of seven children born to the late Moira (née McDermott) and John Conrad O'Hara in Toronto, Ontario, Canada, and she does not have an identical or fraternal twin sibling.
As a versatile Canadian actress and comedian best known for her work on SCTV and in films by Tim Burton, O'Hara's family background is often of interest to fans. The following profile details her lineage and place among her siblings, clarifying her twin status with available evidence.