Who are the main characters?

As in the previous five novels in Cynthia Voigt's Tillerman Cycle (Homecoming, Dicey's Song, A Solitary Blue, The Runner, and Come a Stranger), the principal characters in Sons From Afar are all members of the Tillerman clan of Crisfield, Maryland, in the late 1980s. (This book was published in 1987.) Unlike in the previous books, however, Voigt turns her attention away from Dicey Tillerman to focus on Dicey's younger brothers, James and Sammy. Introverted James, a fifteen-year-old, is intelligent but embarrassed about it. He joins the baseball team in an effort to look athletic and well-rounded on college applications but otherwise has little interest in the sport.
Sammy, a twelve-year-old, is an effective contrast to James. He is athletic and self-confident but cares little about matters of the mind. Both brothers are in the care of their maternal "Gram," Abigail, who shares a number of character traits with the mostly absent Dicey: she is independent and feisty, even eccentric, but loyal to her family above all. Sammy is quick to fight, and he has a difficult time dealing with his mother's abandonment of her children.
The brothers share the home with their fourteen-year-old sister, Maybeth, who is pretty and in many ways reminiscent of her mother. She struggles with her schoolwork in every class but home economics.
The Tillerman Cycle concluded with 1989's Seventeen Against the Dealer.
https://marveloustales.com/2015/03/09/book-review-sons-from-afar-tillerman-cycle/

https://www.kirkusreviews.com/book-reviews/cynthia-voigt/come-a-stranger/

https://www.simonandschuster.com/series/The-Tillerman-Cycle