Ok to sort out some confusion about the Tinkers-
Tinkers are basically gypsy's who travel, collect, fix and sell things from place to place. Very tight family structures but unscrupulous with outsiders, Tinkers are not the most trusting or trusted folks.
Gally stepped into a fight between two men who killed each other over a woman. The gunfight also scattered the other members of Maggotville.
So who are these folks.
Where the older man was married to Elroy's "grandma" who was wounded in the gunfight and was worked on by Wolf.
But she's really not Elroy's grandmother (athough this does suggest in-breeding) but his Aunt. "Grandmother" is the older sister of Clara, who is Elroy's mom.
Based on Elroy's testimony, the woman that the party has met in the junkyard, is Clara. She is the wife of the younger man who was killed in the gunfight witnessed by Gally.
Marg is "Grandma's" daughter. She's probably the one we heard screaming in the sewer.
There are two other children, Meg and Bobby, but we don't know who they are children of, probably "Grandma".
Angie, was the new woman brought into fold, a second wife perhaps for the younger man or "another token woman" for the Tinkers. It seems the men were fighting over her when shots were fired.