What is your theory for Summerhall in 259 ? ( spoilers extended ) I think we will get an answer in Fire and Blood 2

Why did they wed if they did not love each other?”

“Your grandsire commanded it. A woods witch had told him that the prince was promised would be born of their line.”

“A woods witch?” Dany was astonished.

“She came to court with Jenny of Oldstones. A stunted thing, grotesque to look upon. A dwarf, most people said, though to Lady Jenny, who always claimed that she was one of the children of the forest.”

“What became of her?”

“Summerhall.” The word was fraught with doom.

Daenerys IV, ADwD 23