Who is Shepley Walker from Little Altars Everywhere and what is their importance?

Shepley Walker is Sidda's father. He is described as a disciplinarian, who avoids his wife as much as possible. When we first meet Shep, he tends to drink too much. Over the course of the novel, we see a man who is afraid to stand up for himself or his children, as he allows Viviane to control the household. In the end, he takes control of his drinking problem and quits.... something Viviane is never able to do.