why would niang tell them they could enter or leave by the back door only? what does this suggest

The house was large and beautiful, but much of it was off-limits to Adeline and her siblings. The living room was only for their father's visitors. They must always enter the house by the back door. The second floor had bedrooms for their father, Niang and their two children. Their bedrooms were located on the third floor. The three older boys would share a room, Adeline and Aunt Baba would share a room and Big Sister and Ye Ye would each have their own bedrooms....We can see that Step children are meant to take an almost servant like role. They are not afforded the same respect as "real" children.