Otha married on March 13, 1828 in Bullitt County, Kentucky to Martha Connell, and on September 21, 1843 also in Bullitt County to Harriet Ash.

Brother of Elizabeth Roby Wilhite.

Brother-in-law of Capt. John Bailey Bolton.

Uncle of John C. Roby.

Otha's father Lawrence Roby purchased in May 1797 from Henry Crist and Nicholas Crist for £100 a tract of 165 acres on Coxes Creek in Bullitt County which included the place where Roby was already residing. In April 1797 he was granted a license to keep a tavern at his house, having entered into bond as the law directed. Also in April 1797 he was appointed overseer of the road leading from his place to Delaneys Ferry, which was between Benjamin Ogden's property and the county line, and the 'hands' living on the east side of the Salt River from Coxes Creek to the mouth of the west fork were ordered to assist, including Nicholas Crist and Elisha Carr. In June 1797 he was appointed overseer of the road running from the Buffalo Crossing of Coxes Creek to the mill being erected by Crist and Briscoe, which post Roby resigned in November 1799. Lawrence Roby died testate with a will written September 2, 1817 which was recorded November 3, 1817. He left his wife Catharine the house and plantation where they resided along with various personal property, and made other bequests to his sons and daughters. Their children were Samuel, Otha, Lawrence, William, Owen, Reason, John, Elizabeth (wife of Abram Wilhite), Polly (wife of Joseph Greenwell), Martha (called Patsy), Katharine (wife of John B. Bolton), Susanna, and Harriet (wife of James Crenshaw).

Otha's grandfather, William Roby of John, who resided in Port Tobacco Hundred, Charles County, Maryland, died testate with a will dated January 2, 1775, which was admitted to probate on March 25, 1775 on the oath of the widow Elizabeth Roby with the notation 'Owen Roby the heir at law being in the backwoods'. Otha's grandmother Elizabeth, wife of William Roby of John, was very likely an elder sister of William Roby Owen (1749-1798).