Stannis looked at the tired woman. Indeed, the childbed was to women what the battlefield was to men – bloody, smelly, full of screams, exhausting and potentially fatal. Her weariness made her look older than her eight and thirty years. To Stannis' eyes this made her look exactly like the grandmother he remembered.
He will NOT kill her. Nor her children. She was neither her mad brother-husband nor raper nephew-son. And she was sort of an aunt to him ...
He will find a way ...
A week later, Kingslanding
"YOU WHAT?! You stupid fucker!" – the King lunged at his blood-brother.
Robert was broader and His was The Fury. Stannis was faster and His was The Frustration. The two brothers pummelled one another, the younger releasing all his pent up resentment.
Three days later, The Gullet
Sporting an impressive shiner and several other bruises Stannis could make out Dragonstone – still only a smudge on the horizon. But his eyes were drawn to the south, in the direction of Massey's Hook. He gazed past the Sharp Point castle on the tip of the peninsula – his thoughts were on his beloved Storms End. The place where he grew up and defended to the brink of death by starvation against the Reachmen lay somewhere to the south of it. Unless he outlived Robert he would never see his ancestral seat ever again.
Surprisingly a flicker of thought had passed through the wine soaked sponge in his ROYAL brother's skull and allowed Stannis to keep his head – Robert's hold on the Iron Throne was too shaky for him to survive being openly a kinslayer. Jon Arryn had managed to commute Stannis' sentence of exile to banishment and confinement to Dragonstone. His setting foot on the mainland – even on the lands sworn to Dragonstone – was to bring about his execution, however.
Stannis gave a mental shrug about his sentence – he was alive – and he could now do his duty to his family. To his wife and two step-children. All subject to the same banishment decree as he was.
"Stannis, I know you want it. Every man does."
"Yes, I want it. But I wish you alive more."
"Let me do it. Men take up the sword and risk their lives in battle for those who they love. And this is how women risk theirs for a man they love."
Thus Shireen was born before the year was out. It was to be his and Rhaella's only child.
Viserys was a child with worrying inclinations. However, the combined firmness exerted by Stannis and tender, loving care given by Rhaella put the lad to rights. The much healthier human environment of Dragonstone compared to the Red Keep under Aerys also helped.
Stannis maintained a small fleet to fight piracy in the waters of the Narrow Sea, assisting the Royal Fleet in this task. He usually commanded Dragonstone's ships himself. Once he was grown enough Viserys accompanied him as his squire. After being visited by the Master of Whispers who made veiled yet evidently seditious suggestions – and knew too much - Stannis forbid Varys from coming to the island ever again. Regardless if this had been a provocation instigated by Robert or the eunuch had been acting on his own, Stannis would neither act against his brother nor endanger his family. He ruthlessly rooted out Varys' "little birds".
The children grew strong and hale. Albeit scared for life Shireen survived her bout of Greyscale, while Daenerys had to endure being called "shorty" by her siblings - her sister quickly becoming the taller of the two spite of being two years younger. After coming of age Viserys became a sellsword in Essos with the Second Sons company.
The couple leaned onto one another admiring the sunset. They were flanked by their two girls, with Danearys on Stannis' arm and Shireen on Rhaella's.
"With Robert dead, Stark in the Black Cells, Renly fleeing to Storms End sending out ravens that Cersei's children are hers by the Kinslayer, I think that we should recall Viserys. He has been in Essos long enough and I wish to keep him close in times like these."
"Yes, my dear."
I know that this is only a laconic sketch of the AU. I leave description of "who wore what", "how they married for duty but discovered their love for one another", "they screamed their names as their reached their peak together" etc. to more skilled writers.
Feel free to run with "the dragon has three heads" scenarios with Viserys and Daenerys and Shireen. Or Viserys marrying Shireen because nobody else would - he loves his sister! Or any other idea that pops into your mind :)
In case you didn't know - Stannis' grandmother was Rhaelle Targaryen - an honest to God, white-blonde violet-eyed (?) Targ; Yes, one is Rhaelle and the other Rhaella ...