It was William Barton who first began to question Caroline Hanks Hitchcock. She poured out a bucket of vitriol in her letters to Tarbell against Barton, but Tarbell, trying to play both sides against the middle, didn't take the bait. To get a first-hand account, here are the relevant Tarbell papers where Hitchcock is concerned.
https://dspace.allegheny.edu/handle/1045...line+Hanks
For more detail on Tarbell's study of the Hanks family I would suggest going to the subject category on the website of her papers and type in "Hanks." I would also suggest doing the same for Barton, given that there are different ways his name is used in her papers.
Best
Rob