Family logistics
Plan a family photo-sorting project
Photo projects stall without a clear order of steps. Deciding on folders, duplicate handling, and backup first means you will not spend a weekend undoing a mistake.
What to check in the answer
Backup should be the first step. Originals stay where they are until you have checked a sorted copy. Any step that touches the shared album should say that your sibling's permission and preferences apply, since you cannot assume you may reorganize it. Tools define duplicates differently, so the plan should say what counts as a duplicate here and how you will confirm before deleting anything.
Where to go from here
Back up all three sources before anything else. Talk to your sibling before you move or rename anything in the shared album. Once the originals are safe and your sibling agrees, work through the sorted copy and check the structure before you treat the project as done.