As with many things in Family history research, you may never really find out the reasons behind what happened.
I'm sure we all share the sense of frustration that brings.
But I think the suggestion from Panda44 of planting a Rose so that you can think of those who've gone, and remember them quietly, and acknowledge them, is a very good idea.
You will know that no-one is gone whilst someone remembers them.
and you are doing this on behalf of your uncle, and also acknowledging the distress your grandfather must have felt.
Added: I have a photograph of my great grandmother, with her husband and children, back in about 1895. They had lost two children in a month very shortly before. And I can see it, in her face. Bless her and them