WESTEROS AU XV: LIFE A DREAM

THE HOLDFAST PRISONER'S DREAM

An ASoIaF/Game of Thrones fusion with...

Calderón de la Barca's play Life a Dream
and
the Rapunzel story

What if... Jaime and Cersei had been raised apart, in different environments, and Jaime had never known the Lannisters?
This is the divergence point around which this narrative revolves.

Like in canon, they're born on the same day, the girl first, the boy clutching her heel. The moon eclipsed the sun, dying the sky the colour of blood, and waves the size of pine-trees lashed against the Westerland coasts. Lord Tywin was told by the servants that all of that were signs: Cersei would be the heiress and Jaime her vassal, who would turn against her and against all the Lannisters, dethroning Tywin by force, to bring bloodshed and misfortune upon the Lannister clan, the Westerlands, and all of Westeros.
And thus, a newborn Jaime was sent to live as a lifetime prisoner in a little run-down holdfast (or fort) near the border with the Reach, raised by its garrison, taught to read and write, playing with sticks and stones, lacking a proper social life... while Cersei lived a more elegant life, with more social interaction and the knowledge of courtly culture which her brother lacks.
Twenty years later, a freckled and fair-haired knight and the dark boy who accompany her meet an odd-eyed imp in an inn near the fort. An adult the size of a child, with slightly pointed ears and an eye each colour. The knight, actually a girl raised as a boy, is on her way to Casterly Rock "to pay back an old debt". The imp has been raised by mummers (circus performers), and he wants to go his own way. Not knowing themselves that well, Brienne of Tarth, her squire Pod Payne, and Tyrion Hill decide to keep each other company for company's sake.
Their path and a thunderstorm lead them to the holdfast, where they find an unkempt and poorly dressed young man in a tower dungeon. Golden-haired and green-eyed, the prisoner Jaime Hill has never seen any living being but the few soldiers stationed in this wasteland and their families. He instantly bonds with the blue-eyed warrior, and they take to each other, the prisoner thinking (like everyone else in this story at first) that she is actually of his own gender.
At Casterly Rock, the betrothal of Lady Cersei and Loras Tyrell is the talk of the halls. Loras's sister Margaery and her husband Renly Baratheon are also staying in the Lannister residence. The fact that her fiancé doesn't display any emotions towards Cersei only serves to kindle the fire in her heart. So unaware is she of the Tyrells' family secret...
For Renly and Loras, and the Tyrells in general, keeping up appearances when it comes to love is everything.
Tywin Lannister is regretting the decisions he made to do off with both his sons, both of them allegedly stillborn. Perhaps he could bring at least Jaime over to court, to see how he will behave himself. If he doesn't, his sister and prospective brother-in-law will be the heirs of Casterly Rock. But will a socially awkward youth raised like a common soldier or sellsword pass the test?
So he contacts the Harrenhal-based renegade maester Qyburn, who knows how to distill so-called "liquid fire" or "firewater" (id est, brandy or eau-de-vie), a potion which takes such hold of the drinker's mind that he will be left for dead.
That evening, Brienne arrives at Casterly Rock, reunites with Renly (whose marriage to another she intends to avenge with a duel) but decides not to draw steel yet, but to become a maidservant at Lady Cersei's service. Her new employer treats the maid very like Cinderella's stepsisters.
Renly and Loras recognize the Maid by the hilt of her sword.
Pod also gets a job as a valet in the Lannister household.
Tyrion the imp gets to stay as an entertainer for the Lannisters.
Meanwhile in the holdfast, Jaime drinks wine laced with liquor, then starts to feel his vitals on fire, to see the room reeling and spinning, then everything turn dark before him as he falls unconscious. The lifeless young prisoner is brought by servants into a carriage, that carries his unconscious form all the way to the Lannister residence.
Imagine his surprise ("Is this the afterlife?") when he wakes up in a scarlet-curtained bed in a grand bedchamber, given a levée, washed clean and clean shaven by servants of both genders, served a feast for breakfast, meeting an old gentleman who claims he's Lord Tywin Lannister and Jaime's father, a young lady the spitting image of his own reflection in the bedchamber mirror (into which, never having seen one before, he has curiously peered) who claims to be his sister, a trio of good-looking foreigners, an army of manservants and maidservants, and a maid very similar to the blue knight he recently met in the holdfast... and these alleged family ties make the young blond a Lannister and the heir to the Westerlands... How can it be?
After several unfortunate fish-out-of-water mishaps, Jaime makes love to his twin sister and lunges at his own father, and thus... all hell breaks loose: the drunken heir fondles Brienne, who challenges Renly to a duel, Renly and Loras come out. Jaime defenestrates Pod into a fountain for contradicting a whim of his ("the things I do for love"), and he is drugged with liquor once more and locked, together with Pod and with the imp (whose identity the Lannister patriarch has discovered), in the old holdfast... Lord Tywin and his daughter (who will not stay and wait in her alcove, but wear a breastplate and wield a spear) go to war against the Reach, whose forces are led by the ménage à trois...
Brienne takes her leave, on her own, to find the fort at the fringe of the intended battlefield and most of the Lannister sellswords, who have deserted, trying to storm it and free their rightful lord...
Meanwhile, the young prisoner wakes up in his tower dungeon, believing that his experiences at Casterly Rock were all just a dream. The arrival of the Maid blurs the distinction between dream and reality: how come the young knight he had seen and sympathized with appeared in that dream as a handmaiden at a ruler's court?
So both Jaime and she, at the head of the deserters (including Pod and Tyrion), will have to fight battles against the two armies encamped on either side...

Ending: Jaime pardons Tywin and Cersei on the battlefield, after having taken them prisoner.
Brienne does the same to Renly and Loras, after defeating the former in a swordfight on the same field.
Pod Payne is killed in battle.
Renly, Loras, and Margaery return to the Reach.
Cersei's betrothal is annulled and delayed, while Jaime and Brienne win the last battle and set sail for Tarth, and the Imp still goes his own way.
Upon reaching the Sapphire Isle, the green-eyed outcast and the freckled lady knight share a passionate kiss of true love.

And thus, upon their brand new life's first day,
to Brienne, Jaime, fond farewell we say,
and wend, from Westeros, back to our world, our way.