In the book A Child Called "It," David has two brothers close to his age, Ron and Stan, who abide by their mother's wishes in ostracizing David. Ron is slightly older, and Stan is a bit younger. They offer no sense of protection or assistance to their brother, likely because they don't want their mother's insane methods of abuse to turn on them.
At least initially, though, their presence is a comfort to David; he realizes that his mother never acts so bizarrely when other people are around. When she resorts to attempting to burn David on the stove, for example, David realizes that he just has to buy enough time for Ron to come home from his Scouts meeting. Their mother manipulates Ron and Stan into believing that their brother deserves his abuse on some level, such as the evening following her threats to burn David alive:
I stood tall. I could hear Mother talking to Ron upstairs, telling him how proud she was of him, and how she didn’t have to worry about Ron becoming like David—a bad boy.
Russell is David's younger brother, and their mother uses him as a prop of sorts to demonstrate her excellence in maternal care. Once when the school forces her to come in to discuss the signs of abuse they have noted, she takes young Russell along:
She told me how she had dressed up to see the principal, with her infant son Russell in her arms. Mother told me how she had explained to the principal how David had an overactive imagination. Mother told him how David had often struck and scratched himself to get attention, since the recent birth of his new brother, Russell.
Russell is trained to "work" for his mother as he gets older, keeping an eye on David for her.
Later, baby Kevin joins their dysfunctional family, and David really adores him:
The only thing that kept me sane was my baby brother Kevin. He was a beautiful baby and I loved him.
It is important to note that David changes the true names of his brothers in his book.