Note that Lucinda’s father, husband, and younger brother were all named Francis Marion Lewis!

Morgan Co., Ky marriage records list the marriage on 8 Jan 1862 of F. M. Lewis and Lucinda Lewis, at Frank Lewis Jr’s by R. C. Day, witnesses John Peyton and Price Lewis.

1870 census of Morgan Co., Ky, Blairs Mill precinct, Bangor P.O., enumerated 20 July, lists on p. 1 as family #7:
Lewis, Marion, 31, farmer; Lucinda, 31; John F., 7; Mary, 6; Ellender, 5; Samuel K., 2. All born in Kentucky.

1880 census of Morgan Co., Ky, West Liberty precinct, enumerated 9 June, lists on p. 21 as family #180:
Lewis, Marion, 40, son-in-law, farmer; Sindia, 40, wife; John, 17, son; Marry, 16, dau; Ellen, 14, dau; Samuel, 12, son; Loucindia, 11, dau; Margrett, 7, dau; Adline, 6, dau; Hanah, 4, dau; Nancy, 2, dau. All born Ky Ky Ky. (Actually, the relationship fields are blank, but there is a single long wiggley line down from lines 7 through 50 apparently intended to function as a ditto indicator.)

Since the daughter Loucindia was not listed in the 1870 census, her age is probably high by a year (although her death certificate also says she was born in 1869.)

The relationship ‘son in law’ for Marion is because the previous household is headed by Lucinda’s widowed mother, Pollly Lewis. The two households are given separate numbers, though.

The following household is headed by Henry Clay Lewis, age 26, with the relationship given as uncle. Henry was Lucinda’s brother, which would make him an uncle of her children, although reporting the head of a household’s relationship to a child in the preceding family is rather unusual.