Tsuntsun was the only son of the family. Since his birth, he had been living in his maternal grandparents' house during weekdays and was taken care of by his grandmother. His parents visited him occasionally during the weekday evenings and took him back home on Friday nights to stay over the weekend. They communicated in Cantonese.

Bohuen was brought up in a monolingual Cantonese-speaking working class family. She has a younger brother who was about two years younger than her. They lived with the child's grandmother and uncle. The child had already started attending a nursery school when data collection started. After school, she was taken care of by her parents and grandmother.

Gakei was also brought up in a monolingual Cantonese-speaking working class family. Her father was a technician in an electronic company and her mother was a housewife. Gakei's parents were born in Hong Kong. The child was not yet enrolled in a nursery during the whole period of data collection. She was entirely taken care of by her mother.

Chunyat was born in Hong Kong and was brought up in a monolingual Cantonese-speaking family. He had not started going to a nursery during the period of data collection. He was the only son in the family. His father was a merchant and his mother taught English in a secondary school. They lived with the child's maternal grandparents.

Jenny was born in Hong Kong and was brought up in a monolingual Cantonese-speaking family. She was the youngest child in the family. She had an elder brother who was ten years older and an elder sister who was four years older. Jenny's father was a businessman and her mother was a housewife. The family employed a Filipino helper, who spoke some Cantonese and English to the children.

Tinfaan was the youngest child in the family. During the first one-and-a-half years from her birth, she was taken care of mostly by a Filipino helper while her mother worked as a school music teacher. After her mother had stopped working in school, Tinfaan was mostly taken care of by her mother. She communicated in Cantonese except when speaking to the Filipino helper, for which she used 'something English-like' (as described by her mother).

Johnny was born in Hong Kong and was brought up in a monolingual Cantonese-speaking family. He was the youngest child in the family and had an elder sister who was seven years older. His father was an engineer and her mother was a typist. The family employed a Thai helper and she spoke Cantonese to the children.