Tommen Baratheon
The younger prince, a gentle, plump little boy who loves his kittens and his sister far more than any thought of crowns.
A soul of House Lannister, born at King's Landing.
The fuller tale
Season Four
Joffrey's little brother, gentler by miles and aware of it, inherits a crown he never asked for and a grandfather who moves fast to make sure grief does not slow down an alliance — he is married to Margaery within the same season his brother dies at her wedding feast. Tywin walks him through what a king owes his lords like a man teaching a child to tie his boots, and Margaery, newly widowed of a husband who barely touched her, starts teaching him a different set of lessons in his bedroom at night, patient and entirely unhurried.
Season Five
Married and besotted, and easy for both his wife and his mother to manage as long as neither one notices the other doing it. Cersei's gamble to rearm the Faith and aim it at the Tyrells backfires immediately: Margaery is arrested on the Sept steps for lying to protect her brother, and Tommen marches the Kingsguard down to get her out, only to be turned away by the High Sparrow with nothing but words — because it turns out a king who has never had to fight for anything does not know how. He spends the back half of the year locked out of both his wife's cell and his own city's temple.
Season Six
King in name only by now, and it shows: he lets Cersei bar him from attending his own wife's trial in the Sept, and it is Margaery who has to send him a warning through the Faith to stay away that morning without saying why. He watches the Sept of Baelor go up from the Red Keep window, a green column of fire that takes Margaery and half the court he has spent two years failing to protect along with it, and once it settles he sets his crown on the table and walks out through the same window, without a word to anyone.
How it ends for them
On the screen. Died when the sept burned (S6·E10)
The gentle boy king watched the Great Sept — and his queen inside it — vanish in green fire from his window. He set down his crown, and stepped quietly out into the air. The last of Cersei's children, as the prophecy promised.
The show gives him the quietest death in a season of loud ones. On the morning of Cersei's trial, Tommen waits at his window for the bells — and instead watches the Great Sept of Baelor, with Margaery and the High Sparrow and half his court inside, erupt in a bloom of green fire across the city. He says nothing. An attendant announces him; he sets the crown carefully on its stand, looks a long moment at the smoke where his wife was, and steps out of the window without drama or sound. Cersei, who burned the sept to save herself from trial, has fulfilled the prophecy's third shroud with her own hands — and her instruction for his body, that he be burned and his ashes interred in the sept's ruins, is as close as the show lets her come to admitting it. In the published books Tommen is alive: still eight, still king, still signing what he is told to sign, with readers left to dread how the novels intend to collect on the same prophecy.
Their chapters, book by book
A Feast for Crows 1 chapter that name them
Where the page and the screen part
The versions diverge on age and therefore on everything. Book Tommen is a small child — his marriage to Margaery is ceremonial, his kingship a rubber stamp, his story so far a hostage's — while the show's aged-up Tommen is old enough to love his queen, defy his mother, and be genuinely complicit in his own manipulation, which gives his arc a moral weight the books reserve for later. The show also hands him decisions the books haven't reached: the crown-Faith alliance and the abolition of trial by combat are television inventions, the latter aimed like a weapon at Cersei's one escape route. As of the published novels his story is all potential energy: a boy king on a poisoned throne, with Maggy's prophecy — gold their crowns, gold their shrouds — hanging over all three of Cersei's children and two installments still unwritten.
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.