What is the theme in The Tie That Binds: A Novel by Kent Haruf?

There's little doubt that loyalty is a major theme of this story, which is first exhibited with Sandy Roscoe refuses to give any information to the reporter from the Denver Post. Not only does Sandy refuse information, he snatches a sheet of paper from the young reporter's notebook and grinds it into the cow manure underfoot. Sandy also says that the reporter should at least learn to say the name, "Goodnough," correctly. To explain this loyalty, Sandy goes back many years to a time when his father, John Roscoe, was six and the Goodnoughs arrived in Colorado as homesteaders. Over the years, John and Edith Goodnough become close, fall in love and endure hardships together though they never marry. Sandy says that when he considers that his father loved Edith Goodnough, he can't help having feelings for her as well.