I think I can straighten this out.
George Robert Robertson (Apr 14, 1849 - Mar 7, 1937) was the son of Alexander Mack Robertson (1819-1888) and Sarah (unknown) (ca. 1823 - ca 1851). He was born in Tennessee, died in Oklahoma City, Oklahoma, and was buried in the Sunny Lane Cemetery, Del City, Oklahoma, Oklahoma.
He married (1) Mary Ann Austin, daughter of Joseph Austin and Eizabeth (unknown), who was born in May 1860 in Evansville, Vanderburgh, Indiana, died December 22, 1883 in Van Buren, Crawford, Arkansas, and was buried in Gill Cemetery, Van Buren, Crawford, Arkansas. Their children were Lilly May and Rosa Bell. In the 1880 Census, they were living as you described, with daughter Lilly May and others, but they were living in Vine Prairie, Crawford, Arkansas at that time.
He married (2) Ida L. Ingram, daughter of Creed Ingram and Sarah L. Sanders, in 1884. She was born on March 20, 1859, died March 20, 1941, and was buried in Sunny Lane Cemetery, Del City, Oklahoma, Oklahoma. Their children were Sarah L., George Robert Jr., Minnie E., Ethel Virginia, Alexander L., and Ray M.
By the way, Alexander Mack Robertson is buried in King Cemetery, Mulberry, Crawford, Arkansas, alongside his daughter Louisa "Lou," George Robert's half-sister and my grandmother's sister.
I've actually amassed a great deal of information regarding this family because Alexander Mack Robertson is my great-grandfather through his third wife, Nora Ellen Baldridge. I'd be happy to share anything I have with you.