I’ve actually started trying to trace where the blood feud goes back to, and there’s actually a couple lines of it coming down. I’m quite sure there will be more threads added.
But where things seem to start: The Seer tells Rumple his son will be fatherless, leading to everything Rumple does. Rumple kills Milah, leading to everything Hook does. Eva trips Cora, leading to everything Cora does. It becomes Snow’s war when Cora kills Eva, and Regina’s when Snow tells Cora about Daniel. George’s grudge against David is sparked by whomever poisoned his wife…if there’s a link to Cora there, that would be fascinating, though it doesn’t become about David personally until he rejects the marriage with Abigail.
And there’s a LOT of killing and attempted killing in between, mostly Cora/Regina vs their own family and vs. Snow’s family. (Cora/Regina are responsible for Snow’s parents/nanny dying, Snow is responsible for Cora/Daniel dying, Cora/Regina actually killed Regina’s parents and Daniel…)
Keeper of Belle's Gold magic, sand dollar, cloaks, purple FTL outfit, spell scroll, library key, copy of Romeo and Juliet, and cry-muffling pillow, Rumple's doll, overcoat, and strength, and The Timeline. My spreadsheet: https://drive.google.com/file/d/0B6r8CySCCWd9R0RUNm4xR3RhMEU/view?usp=sharing