Do you think anyone else would come forward and support Jon Snow for the battle against Boltons
I don't remember the story much since I read the books while ago.
But in the books Sir Davos goes to white harbor to recruit manderly's to stannis/ jon's side against the boltons.
Then manderly says boltons got ARYA( jeyne pool dressed as arya wedded to ramsay but no one knows) so they won't oppose since boltons got a bigger claim and manderley's son's are being held captive at the freys (as I remember) UNLESS davos & stannis can find Rickon Stark (the youngest) with the direwolf(to make sure that he's rickon). And one points out that rickon has gone to island of skagos. (A man-eater tribe lives there as I remember(only rumoors)) So davos goes to skagos.
SO THERE ARE MANDERLEY AT WHITE HARBOUR.
Then there are umbers. Umbers are loyal to the starks. Hother Umber (whoresbane) swears allegiance to the boltons only because his nephew, Greatjon Umber(lord of Last Hearth) is held captive at the twins.
But later in the dance of dragons whoresbane's brother, Mors Crowfood gathers up theon & Jeyne Pool(known as arya atm) and goes to stannis and makes a pact with him.
SO THERE ARE UMBERS FROM LAST HEARTH.
Then there are flints. Cerwyns. Mormonts from Bear Islands. Howland Reed and his crannogmen from Deepwood Motte.
The houses near to the pyke islands have been weakened by the greyjoys since balon greyjoy attacked them but still they have some numbers.
So almost all of the bannermen of starks are still behind them except for the BOLTONS & the KARSTARKS of Karhold.
But I don't think there'll be much of a fight between boltons & Jon. The nothern bannermen will turn against boltons and they'll be helpless if it comes to that.
Don't know what'll happen in the TV Show though