|Hold it right there, outlaw!|
This article is littered with spoilers, so I reckon you might ought'a mosey on down the road if you don't want to read any plot details.
He is the son of Grace Anderson.
Marston has very little interaction with Ralph, and he finds only a pool of blood with an arm bone, foot bone, and a shoe as evidence of the boy's demise. This is all that's left after Randall Forrester devours him.