(Spoilers Extended) Why GRRM always needed Two Sons of Rhaegar
The idea of Young Griff/fAegon is something GRRM set up a very long time ago, certainly in 1998 during A Clash of Kings
> A mummer's dragon, you said. What is a mummer's dragon, pray?"
> "A cloth dragon on poles," Dany explained. "Mummers use them in their follies, to give the heroes something to fight."
And in 2000, GRRM basically gave it away;
> "I was wondering if you could answer (or take the "fifth") one teeny little question I've been dying to ask for the past year: Are Aegon and Rhaenys, Elia's children, well and truly dead?"
> GRRM: "All I have to say is that there is absolutely no doubt that little Princess Rhaenys was dragged from beneath her father's bed and slain."
So, Aegon surviving was a part of the plan for a long time. However....
Whats the point?
The central mystery of the series is R+L=J and Jon being Rhaegar’s son, and therefore being able to ride a dragon, play some magical role in the Long Night, and possess a plausible claim to the Iron Throne.
So why did GRRM feel the need to introduce another surviving "son of Rhaegar" plotline? Why spend so much narrative energy on "Aha! Rhaegar’s other son is (most likely not) alive, but this other guy is impersonating him"?
It just feels a bit weird. Why couldn't Jon simply do the story beats Young Griff is being set up to do? Then it hit me.
It's the name, stupid
When the show said Jon's birth name was Aegon, a lot of people thought it was totally ridiculous and D&D just made it up. Two Aegons? But I think the books may make that duplication very meaningful.
I made a post about this before, but a theory that's been out there for a while is that Lyanna named Jon, not Rhaegar. Rhaegar probably believed the child would be a girl, which is why after Aegon is born, he looks at Dany and says;
> He looked up when he said it and his eyes met Dany's, and it seemed as if he saw her standing there beyond the door. "There must be one more," he said, though whether he was speaking to her or the woman in the bed she could not say. "The dragon has three heads."
A girl completing the original three heads of the dragon alongside Rhaenys and Aegon. That’s why his first two children were named after the Conqueror siblings.
Now try to imagine Lyanna's position at the Tower of Joy after Jon is born;
Rhaegar is dead.
Elia, Rhaenys and Aegon are dead.
The child expected to be a girl is instead a boy.
So Lyanna just chooses the quintessential male Targaryen royal name for her son, and the one Rhaegar associated with prophecy, kingship, and the PtwP;
> "Aegon," he said to a woman nursing a newborn babe in a great wooden bed. "What better name for a king?"
> "Will you make a song for him?" the woman asked.
> "He has a song," the man replied. "He is the prince that was promised, and his is the song of ice and fire."
I think Young Griff needs to appear first as "Aegon VI," a term which GRRM himself uses when discussing characters from the books who never appeared in the show.
> There are characters who never made it onto the screen at all, and others who died in the show but still live in the books… so if nothing else, the readers will learn what happened to Jeyne Poole, Lady Stoneheart, Penny and her pig, Skahaz Shavepate, Arianne Martell, Darkstar, Victarion Greyjoy, Ser Garlan the Gallant, Aegon VI, and a myriad of other characters both great and small that viewers of the show never had the chance to meet.
Young Griff will appear as the returned son of Rhaegar. He introduces to Westeros the idea that a son of Rhaegar survived and is here to deliver them from disaster
But he is a false savior, since we know he is one of the "lies" Dany will slay. And, so after his fall, Westeros will descend even further into chaos due to figures like Euron, and with the Long Night arriving, the real hidden heir emerges;
Jon as Aegon VII.
Seven Kingdoms, Seven Gods and a Seventh Aegon to fight in the Long Night. I think that's why GRRM always have needed both plotlines simultaneously, and two sons of Rhaegar