How many children were in Lizabeth's family?

We are not given information as to the number or ages of Lizabeth's older siblings, but we know that she has a brother Joey, and two younger siblings, who are described as babies, living with a relative.

By the time I was fourteen, my brother Joey and I were the only children left at our house, the older ones having left home for early marriage or the lure of the city, and the two babies having been sent to relatives who might care for them better than we.