Mark Twain (1835-1910) is our fifth cousin three times removed. Our common ancestors are Josiah Furman, Jr. (1652-1742) and Sarah Strickland (1645-1742). Josiah and Sarah are our 7th great grandparents and Mark Twain’s 4th great grandparents. Josiah and Sarah had six children. Their daughter, Martha Furman (1691-1752), is our direct ancestor; she married Edward Hart (ca 1687-1752) and they were the parents of John “Signer of the Declaration of Independence” Hart. Josiah and Sarah’s daughter Mercy (1686-1758) is the 3rd great grandmother of Samuel “Mark Twain” Clemens.
Here is the path from Mark Twain to Josiah and Sarah Furman: Mark Twain → John Marshall Clemens → Samuel Clemens → Elizabeth Moore Clemens → Gershom Moore → Mercy Furman Moore → Josiah Furman, Jr. and Sarah Strickland
Here is the path from Abbott siblings to Josiah and Sarah Furman: Abbott Sibling → RWA → Vera Esler Abbott → Martha Tappan Esler → William Tappan → Sarah Hart Tappan → Daniel Scudder Hart → John Hart → Martha Furman Hart → Josiah Furman, Jr. and Sarah Strickland
It may be that if the families are fully worked out (all the children and marriages added) that there are other connections. There are also reports that we are related to Walt Whitman. The proposed connection for that relationship does not hold up to close scrutiny. We may be some degree of cousin to Whitman, but that is not worked out.