Dickon Tarly
Samwell's younger brother, everything their father wanted in a son: strong, martial, and heir to Horn Hill in Sam's place.
A soul born at Horn Hill, sworn to House Tarly.
The fuller tale
Season Six
The son his father actually wanted, home on leave and polite about it, letting Randyll's insults to Sam land without adding any of his own. He says little at the dinner table beyond civil nothings to Gilly and mild agreement with whatever his father decides, comfortable in a house built entirely around his approval. It is a small, unremarkable role next to Sam's — which is rather the point: everything comes easily to Dickon that never came easily to his brother, and he has never once had to notice.
Season Seven
Fighting under his father's banner once Horn Hill turns its coat to Cersei, present for the sack of Highgarden and taken prisoner with him when Daenerys's dragon catches the Lannister column on the road home. Given the chance to live if he kneels, he starts to take it — offers his sword, tries to save them both — until his father calls it cowardice to his face. Dickon takes the offer back rather than wear that word, and burns beside Randyll moments later, dutiful to a fault and loyal to a man who was never once loyal to him.
How it ends for them
On the screen. Fell after the Reach campaign (S7·E5)
The dutiful heir of Horn Hill stepped forward to share his father's sentence, to Randyll's pride and Sam's grief. Dracarys took the future of House Tarly along with its past.
Show-only, and chosen with open eyes. After the Goldroad rout, Daenerys offers the captured survivors their lives for fealty; Randyll refuses and is sentenced to burn. Dickon announces that his father does not stand alone — over Randyll's single, startled attempt to order him back into the ranks of the living — and refuses the knee in his turn. Tyrion pleads the house's future; Daenerys declines to make exceptions; Drogon executes them together, and House Tarly's past and future go up in one column of flame while its true heir, a continent away, shelves books at the Citadel. In the published novels Dickon is alive at Horn Hill — a boy with a Valyrian sword in his future and no dragons anywhere near him.
Their chapters, book by book
Where the page and the screen part
In the books Dickon is years younger and entirely offstage — a name in Sam's chapters, a betrothal in House Tarly's ledgers, the heir-presumptive of a house whose lord is alive and scheming in King's Landing. The Goldroad field, the choice, and the fire are all show; the books have burned no Tarlys. The show also flattered him upward in age and agency to make the sacrifice legible — book Dickon is a child who has never seen a battlefield, which would have made the same scene an atrocity rather than a choice.
Their journey
Where the two tellings send them to the same place the road runs whole; where they part, the screen keeps the left and the books the right.