Considering she was so far away from the line of succession as to have no claim to the throne of Quel’Thalas, I don’t think she was Kael’thas’ niece. But she is still a Sunstrider.
The main line of Arathor hasn’t ruled anything in the Arathi Highlands since 1800 years prior to the First War.
That is by definition not a retcon. A retcon would imply they are retroactively changing this, but Marran is an addition to the lore. She is no more a retcon than both Arthas and Calia were.
Galen was Thoras’ son, not Danath’s. Neither were ever stated to be the last of the Trollbane family, the closest to that is Skuerto’s line in Cata wanting Danath to return from Outland.
He’s probably in his 60s, so not too old in the slightest.
So they magically sprung up from the earth with no mothers or grandparents to speak of?
We don’t at all. For the Wrynns we know Anduin, Varian, Llane, Barathen and Landan. That’s hardly a full “familiar tree of the Wrynn family”, of the Proudmoores we only know Daelin, Jaina, Derek and Tandred. For Greymane we only know of Genn, his father Archibald and Tess and Liam.
Not counting the wives, of course, as they married into these houses.
They did with Tess and Liam, they did with Mia, they did with all of the families of these royal (noble in the case of Proudmoore) houses when the time came to expand on their lore.
I don’t know where you are from Twili, but as a quick example of this, there are 63 people in line to the British throne of succession and that includes the King of Norway.
