Though the protagonist has a mother and two siblings, he believes he’s alone in the world for most of the novel. It takes him being in jail and learning that his infamy has narrowed his little sister’s life opportunities to realize that his actions affect his family. However, the protagonist prefers to separate himself from his family. His family reminds him of his own shame.
Although Peggy describes working for the Daltons as being part of their family, this is true only for her because she is white; the Daltons’ underlying racism means that Bigger could never be part of the family.