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- Abraham Lincoln pardoned President Joe Biden's great-great-grandfather, Moses J. Robinette, in 1864.
- Robinette was convicted after a fight with an army colleague during the Civil War, documents show.
- He was pardoned after receiving support from several army officers and a West Virginia senator.
President Joe Biden's former boss, ex-President Barack Obama, used to say that his favorite American president was Abraham Lincoln, who kept the nation from splintering during the Civil War. But, on this Presidents Day, Biden may have a reason to show Lincoln some gratitude.