Orphan Guo Dangye celebrates her foster mother Wang Cunxian's 60th birthday in Datong city, Shanxi province. Zhang Meixia / for China Daily

DATONG, Shanxi - Warm winter sunshine spilled through the window of a small yaodong (cave dwelling) in Sancha, a village like any other on North China's Loess Plateau.

Basking in the sunlight, 7-year-old Dang Xuben sat cross-legged on the kang (traditional clay bed) by the window and stared blankly at the old woman beside him.

"Xuben, call me granny," 70-year-old Cai Yuhua murmured, while patting the boy's arms with her wrinkled hands.

Dang was abandoned on the street when his biological parents discovered he was born with an intellectual disability. He became Cai's youngest foster child six years ago.

Also in the room was 19-year-old Dang Mingming, another of Cai's foster children, who has lived with the woman for 16 years. She also has an intellectual disability that hinders her communication.

"Both of them don't speak most of the time. But the occasional words they utter, like 'mommy' or 'granny', always make me smile," Cai said.

In 1968, Cai's newborn died of illness. To heal the emotional wounds, Cai and her husband brought home an orphan from the Datong Institute of Social Welfare.

"The sorrow was gone when I breast-fed the baby girl," Cai said. "I treated her as if she were my own daughter."