Revealing mistake: On her first evening at the ranch Susannah watches Tristan breaking in a mare. When he falls on the ground you can see that he merely climbs off instead of being thrown. (00:18:00)
Revealing mistake: When Tristan takes revenge for his brother and scalps two German soldiers you can see that his knife just goes through the hair. (00:44:25)
Revealing mistake: When Tristan kill the guy in the liquor storage and the hay fork goes through his chest, you can see that parts of the hay fork's tines closest to his body are not covered with blood. (01:51:05)
Answer: There's nothing to tell us who the listener is. Your theory that it's probably a family member seems entirely reasonable, but there's nothing in the film that would allow the identity of the listener to be narrowed down any further than that.
Tailkinker ★