Who are "the twins" in the book, Whale: A Novel?

The twins are twin sisters who own a bar and help raise Chunhui. When they were young, they performed in the circus with Jumbo. However, when the elephant was startled, Jumbo crushed the pelvis of the older twin. They agree to move to Pyeongdae, after Geumbok opens the café. Years later, when the younger twin is killed in an accident, the older twin becomes inhabited by the spirit of her sister. The twins live in one body and bicker continuously with one another until they commit suicide.