That isn't really theory anymore. That has been established by multiple pieces of the story. Jon just doesn't know it yet.Learned a lot these first episodes. This is the theory the Stark kid (3 eyed Raven) Bran Stark knows all and will eventually tell Jon Snow his true identity. Ned Stark's sister was his mother and Ned raised him as his own bastard son for protection.
Theory is Rhaegar Targaryen who died long ago and was respected prince and warrior, also Mad Kings first son and brother to Dany (dragon queen) making Jon and Dany aunt and nephew,
The Targaryen's interbred keeping bloodline in family and because Dany wasn't born yet she was late, Rhaegar ended up fathering child with Ned Starks sister. The child was in great danger and would have been killed if found out so to protect Jon (child), Ned Stark promised his sister to raise him as his own bastard son. So Jon Snow actually Targaryen is half Stark/ Targaryen,
Its getting interesting for sure.
This year everything seems to be time warping, Like Jon's trip to Dragonstone I'm sure it has to be time constraints on finishing story by end of season 8. Keeping the cast together over 8 seasons in itself is a challenge and everyone is ageing.The timeline is hard to fathom sometimes.
You have to assume that weeks or months have passed between events on the show. Maybe it would help if they had on the show "3 weeks later" when they jump to another scene.The timeline is hard to fathom sometimes. The Unsullied and the Dornesh armies left via their Iron Islands armada and Slavers Bay ships. Euron decimates the ships with the Dorne troops and the Sand Snakes and returns back to Kings Landing, gifts in hand. He has time to parade through Kings Landing, present the Queen with the killer of her only daughter, then heads off to dispatch the Unsullied's fleet offshore of Castlery Rock. Euron Greyjoy must command the fastest fleet ever seen in Westros to be able to make it around Dorne and Oldtown, a significant distance. Plus, Euron needed to sail past Dragonstone and three adult dragons. There should have been massive losses and if nothing else, a fleet that large should have been observed and Ravens dispatched to the Unsullied to warn them that Euron's on the way. Or am I overthinking this?