In the US the copyright law has changed over the years and I guess one has to go back to what the law was when the photographs were taken. I did a bunch of research a couple years ago when I acquired several hundred processed 4X5 negatives that were in the home of a friend. She had purchased the home from a retired photographer back in the late 80's. He had just left his negatives behind. The negatives were from the 1950's through the 1970's of local functions with boy scouts, news paper stories around my local area, and lots of weddings. I found some 4X5 negatives taken of a good friend of mine when he was in the scouts in the 1960's...pictures of himself he had never seen.
My desire was to get the wedding negatives into the hands of those married couples or their descendants. I considered scanning and posting them on my pbase site, but after trying to slog through the copyright laws, I gave the idea up. The photographer is now deceased but his son and daughter are alive and in their 60's. I have not tried to contact them as they do not live in my area (I have not tried to locate them).
As the law stands, I believe, I own the physical property - meaning, I own the 4X5" plastic sheets and the silver emulsion coating on them. The family of the photographer has no right to them - but - they do own the rights to the image that has been formed their in.
I may contact the family of the photographer just to get a feel for their desire. I am guessing they probably have no idea that their fathers photographs still exist, and they may or may not care. They are probably not worth anything (they are really not good images compositionally) other than historical or sentimental.