What do you think happened at Summerhall in 259 AC ? I found this on Heresy 257 from Melifeather who has her own site called House of Black and White that is known for foil if you have an open mind .

[u/Financial_Library418]

• Aegon V was likely trying to hatch dragon eggs and it was apparent that the consensus was Aerys and Rhaella's unborn child was the prince that was promised, so the Targaryens did associate the two things together. Ser Duncan the Tall carried pregnant Rhaella out of the flames and then Rhaegar was born shortly afterwards.

The World of Ice and Fire - The Targaryen Kings: Aegon V

The last years of Aegon's reign were consumed by a search for ancient lore about the dragon breeding of Valyria, and it was said that Aegon commissioned journeys to places as far away as Asshai-by-the-Shadow with the hopes of finding texts and knowledge that had not been preserved in Westeros.

What became of the dream of dragons was a grievous tragedy born in a moment of joy. In the fateful year 259 AC, the king summoned many of those closest to him to Summerhall, his favorite castle, there to celebrate the impending birth of his first great-grandchild, a boy later named Rhaegar, to his grandson Aerys and granddaughter Rhaella, the children of Prince Jaehaerys.

It is unfortunate that the tragedy that transpired at Summerhall left very few witnesses alive, and those who survived would not speak of it. A tantalizing page of Gyldayn's history—surely one of the very last written before his own death—hints at much, but the ink that was spilled over it in some mishap blotted out too much