Could you also provide a link to the other profile? There is only a link to one profile here. Also, it would be helpful for us assisting if the profile of your grandfather that you list was also "public", otherwise you'll have to initiate the merge.
Once a merge is initiated, you'll have to approve it on your side, and they'll have to approve it on the other side. Once merged, you can then resolve the duplications by matching and merging the rest. You may want to send the profile owner Private User a collaboration request. Although, being that close, you might be within the family group.