Domeric Bolton

"I had a brother once. Domeric. I think you would've liked him. He played the harp, and liked books. But he fell ill, unfortunately. It was terrible, to lose a brother so young. We buried him beneath the Dreadfort."

- Ramsay Snow

Domeric Bolton is an unseen character in Game of Thrones. He was the heir of House Bolton until his death.

Biography
Domeric Bolton was the only true born son and heir of Lord Roose Bolton, the Lord of the Dreadfort. He was a harpist and very well-read. As a young man, he "fell ill", died, and was buried underneath the Dreadfort. Following his death, Lord Bolton's only living offspring is Ramsay Snow, his bastard son, who has since been legitimized as Ramsay Bolton.

Behind the scenes
Domeric Bolton has only been indirectly mentioned in press interviews by Iwan Rheon and Michael McElhatton  as well as George R.R. Martin in the "Bastards of Westeros" promotional video.

"Iron From Ice", episode 1 of Game of Thrones: A Telltale Games Series, features cut dialogue of Ramsay mentioning Domeric's death to Ethan Forrester and his mother, remarking sarcastically that he "fell ill" and mockingly expressing sorrow.

In the books
In the A Song of Ice and Fire novels, Domeric Bolton was the only son and heir of Lord Roose Bolton and Lady Bethany Ryswell, his second wife. According to Roose, Domeric was quiet but accomplished; he read history, played the harp and rode horses as if born on the saddle. Domeric's mother's younger sister, Lady Barbrey Dustin, was quite fond of him as he had served as a page for her at Barrowton. He also served as a squire for Lord Redfort in the Vale, who said Domeric had the makings of a tournament champion. Domeric enjoyed the company of Redfort's sons in the Vale and, longing for a brother of his own, rode up the Weeping Water to seek out his bastard half-brother despite his father's forbidding it.

According to the Dreadfort's maester, Uthor, Domeric died of a sickness of the bowels. Reek once heard Skinner (one of the Bastard's Boys) say that Ramsay had killed his trueborn brother, but he had never dared to believe it. Roose and Lady Dustin, among others, strongly suspect Ramsay murdered Domeric with poison to take his place as Roose's heir. In view of Ramsay's personality, it is very likely that the taboo of kinslaying means nothing to him, and that he indeed murdered Domeric. Roose, while telling Reek about Domeric, speculates that Ramsay will also murder any trueborn siblings that Walda will give birth to.