Partner software for tree fragments?

Family Tree has hundreds of thousands, if not millions of tree fragments belonging to the descendancies of a small number of early American immigrants. These fragments are not yet attached where they belong, obviously, or they would not be fragments. Also, many fragments are duplicates. This is the natural result of genealogy building from the bottom up, from millions of contributors working from themselves back in time.

To assemble these fragments into working sets, and join them, what partner software or 3rd party program would be most helpful?

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