The first one is probably my favourite Jon x Sansa fic. It is a canon AU in which Jon abandons the NIght’s Watch to join Robb’s cause, and ends up spiriting Sansa away from Kings Landing. I find both Jon and Sansa very much in character, and the story deals beautifully with the apparition of their feelings while they still believe each other to be siblings. A relatively short read, but complete in itself, and overall delightful !
“Found in Forbidden Nights”, by the lovely alienor_woods
http://archiveofourown.org/works/968367/chapters/1901351
The second one is by a well-known author (she wrote “Love and Honour”, THAT epic Ned x Cat fanfic), but her first Jon x Sansa story. It is a modern AU, in which Jon and Sansa are not related. It however still deals very well with the theme of Jon’s identity, and how he interacts with Cat. It is maybe a bit less Jon x Sansa centric than some other pics, but it deals beautifully with the whole Star family’s reaction to Jon and Sansa’s relationship.
“Bluberry Syrup”, by the very talented DKNC
https://archiveofourown.org/works/6468172