Cao Gong and Dao Fang, women of the Han harem
The Book of Han records a "对食" (ate facing each other) bond between Cao Gong and Dao Fang, two women in the harem of Emperor Cheng of Han. The commentator Ying Shao explained "对食" refers to a marriage-like bonding between two people in the imperial harem - either two women or a woman and an eunuch. 1
From Chapter 97 of The Book of Han "Record of Imperial Relatives By Marriage, Section 67B":2
The official Jie Guang reported (to Emperor Ai): "I heard Fair Lady Xu and Cao Gong who is an aide in the Center Palace, both received the favor of Emperor Cheng (the previous emperor) and produced sons, but the children have disappeared mysteriously. I sent my aides to question those who knew of the matter. They took them to Ji Wu, the deputy of the palace prison. Among them were the fomer palace attendants Wang Shun, Wu Gong, Jin Yan; the official maidservants Cao Xiao, Dao Fang and Zhang Qi, the attendants of the former Imperial Wife Zhao - Yu Kezi, Wang Pian, Zang Jian etc. They all said Cao Gong knew the affairs of men and women and that she was formerly assigned to the Center Palace as a learning aide. She was well-versed in The Book of Poetry and served instructed the empress. Fang and Gong ate facing each other...