Epilogue
Centuries later, during a deep cleaning of Castle Dunham, three very old paintings were found. The first was of a golden dragon with the Old High Valyrian glyphs saying "Syrax" on the back. The second was done in late Targaryen of Westeros style and was of a silver haired pale blue violet eyed woman in an elaborate court dress embroidered with dragons and falcons on it. On the back it said "Queen Aemma Arryn". The final painting was of a family whose eldest members, one was of a silver haired, violet eyed woman and the other a dark haired man with one emerald green and one sapphire blue eye. With this painting there was a note written on vellum and in Old High Valyrian.
"To our dearest niece and cousin,
We've heard it isn't in Dane or Anglo-Saxon tradition to have portraits painted but we wanted to send a painter to you to have one of your family to join the portraits you have of your dear mother and dragon. Think of it as a gift from us for your progenity.
With endless love,
Your Uncle, Daemon Targaryen
And
Cousin Rhaenys Targaryen Velaryon"
After a search of historical records, it was found out that Daemon Targaryen was the younger brother of King Viserys Kingdomfall, the King who brought down the Seven Kingdoms and who was still considered to be the absolute worst ruler to have ever had power anywhere in Westeros. They also learned that he was the great grandfather of Lady Alysa Fyre, conqueror of the Vale and Crownlands.
As for Rhaenys Targaryen Velaryon, they learned that she was once considered the potential heir to the Iron Throne since her father had been the Old King's eldest son. However, her grandfather chose to name his second son's eldest heir after their respective fathers had died. She had been known as "the Queen Who Never Was" and was the wife of the richest man in Westeros before they moved to Volantis. She was also the mother of Lady Laena, Daemon Targaryen's wife and mother of his children.
This helped researchers figure out who the mysterious cousin/ niece was. They learned that she was the only child born to King Viserys and his first wife, Queen Aemma Arryn that survived the cradle. She had been given a dragon egg at birth that hatched into the golden dragon she would later name Syrax and would later go on to be the youngest dragonrider in her family history. In quick succession, her father would murder her mother, name her his heir and then wed her maid before banishing her for life and imprisoning her dragon. This was Rhaenyra Targaryen or, as she was later known, Countess Nyra the Unburnt and great matriarch of the Dunfire family.
With this knowledge, they were able to identify the others in the image based on other historical records.
Shortly after this information came out, the Dunfire's were blessed with a daughter who was born with the same violet eyes and silver hair as Countess Nyra so they named their daughter Rhaenyra, in her honor.
Years later, Lady Rhaenyra would attend University in King's Landing where she would meet Crown Prince Daemon of New Valyria. The two would fall in love and eventually go on to marry.
Prince Daemon would gift his unburnt bride a golden dragon egg so that someday she could fly beside him, on her own dragon. It would hatch that very day and she would name it after her namesake's long lost dragon, Syrax. The Prince, who had also named his red dragon after his own namesake's, would be overjoyed.
Finally Prince Daemon and Princess Rhaenyra were able to have their happily ever after together, though they were a different Prince Daemon and Princess Rhaenyra than the Gods' had originally intended. It was their combined blood of dragonrider and unburnt, that when the Long Night came again, would squash the Night King once and for all.
Meanwhile in the afterlife in paradise, Countess Nyra, Earl Sihtric, Prince Daemon, Lady Laena, Princess Rhaenys, Lord Corlys and Queen Aemma looked down on their descendants with endless pride. The road had been long and hard but, in the end, everything worked out well.
As for Viserys, well, the Gods' decided to punish him even more. They let him see the doppelgangers of his brother and daughter as they grew up, their eventual meeting, courtship, marriage, children, coronation and their joys flying through the skies on their dragons.
He raged and raged seeing Daemon with Rhaenyra as he never wanted "Maegor come again" anywhere near "his beloved little girl" nor had he ever wanted her to have access to her dragon again.
While yes, technically it was an heir of his blood that was "promised" in the Song of Ice and Fire, it was truly Daemon and Rhaenyra's blood that allowed the heir to thrive.
Viserys never did learn that Queen Rhaenyra was his Rhaenyra's distant great granddaughter nor that King Daemon was Daemon's distant great grandson.
When King Daemon and Queen Rhaenyra did die of old age, they were able to meet their namesakes who were incredibly pleased with them, just like the Gods' were. Their union had ultimately saved the world.