I was recently in yet another discussion on what to make of the end to the Liam Neeson Rob Roy movie.

PLOT SPOILER-> if not yet seen the movie!!!

In it, Montrose leans over the body and takes the locket from around Archie's neck. In the locket is a picture of Archie's mother.
Within the plot/subplot, Archie is a bastard (in the actual "illegitimate child" sense), and doesn't know who his father really is.
I have ALWAYS taken the end to mean that Montrose is the actual father of Cunningham, which explains why he takes care of him and extends his SO much leyway. Am I off basis on this one? Am I over/misreading this part of the movie?