Robert married Margaret on 30 Oct 1868 in Johnson Co, IN. They had one son, Arthur G. After her death in 1878 he married Sarah Catherine "Sallie" Covert 31 Jan 1882, and they had a daughter, Roxie C. Roxie married Charles Edgar Bowen and had two children: Helen & Mark Edward.

The Franklin Evening Star, Franklin IN -Mon, 26 Apr 1926, pg 11
R. P. HAMILTON DIES AT AGE OF 87; WAS ILL FOR SIX YEARS
Funeral Services to be at Late Home Tuesday Morning
      Robert Pearson Hamilton, 87 years old, died Saturday evening at 7 o’clock at his home on South Main Street after a long illness attending over six years, which had kept him bedfast since Christmas.
      His death removes one of the older residents of the county, a man whose boyhood goes back to the pioneer days of this part of the state. He was the last member of a family of twelve children.
      Funeral services will be held Tuesday morning at 10 o’clock at the late home, 199 South Main street, and the Rev. K. Palmer Miller will be in charge. Burial will be in Greenlawn cemetery.
      Mr. Hamilton was born in Union township, January 31, 1839k being the eleventh of twelve children born to Micajah and Elizabeth (Luyster) Hamilton.
                                                      Enlisted in Army
      After a boyhood spent in this county, Mr. Hamilton emigrated to Kansas in the fall of 1860, returning to Indiana a year later to enlist in the Union army in August, 1862, as a member of Company E, Seventh Regiment Indiana Infantry. At the discharge o the Seventh Regiment in 1864 he was transferred to the Nineteenth Indiana infantry and was mustered out of service near Washington, D.C. May 31, 1865, having served almost three years and passing through the battles of Antietam, Second Bull Run, Petersburgh [sic], the Wilderness campaign, and on to Richmond, and was at the final surrender at Appomattox.
      After the war Mr. Hamilton returned to Johnson county and bought a farm. Later, from 1876 to 1878, he was in Florida, but came back to farming in Johnson county, and in 1887 took up a farm southeast of Franklin, in Needham township. This he occupied until 1920, when he came to Franklin to live, retiring from active work.
      Mr. Hamilton was twice married, the first time to Margaret J. Graham, October 30, 1868. Mrs. Hamilton dying in 1878, Mr. Hamilton married again January 31, 1882, to Sallie C. Covert. She survives her husband together with one daughter, Roxie C., now Mrs. Charles E. Bowen.
      Mr. Hamilton’s early church affiliations were with the Shiloh Presbyterian church, later being transferred to the Franklin Presbyterian church.

History of Johnson County, Indiana, D. D. Banta, 1888
ROBERT P. HAMILTON, a leading farmer of Needham Township, Johnson County, Ind., Living one and one-half miles southeast from Franklin, on the Edinburg state road, was born in Union Township, Johnson County, Ind., on January 31, 1839, and was the eleventh of twelve children, born to Micajah and Elizabeth Luyster.
      The father was born in Culpeper County, Va., in 1797, and died May 5, 1878. The mother was born in 1797, and died January 7, 1884. The father was of English, and the mother of Dutch, extraction. When a boy the father left Virginia, and settled in Mercer County, Ky. His father [Theophilus Hambleton] dying when he was quite young, he was early thrown upon his own resources, being "bound out" soon after the family reached Kentucky, to Garrett Cozine, and during his teens was a wagoner, and drove a six-horse team from Kentucky to the inland towns of the southern states. In the summer of 1834 he came to Johnson County, and entered 240 acres of land, in Section 26, and immediately moved his family from Kentucky, but did not locate on his 240-acre farm until 1837. He followed farming as a life vocation, and was a member of Shiloh Presbyterian Church. He married Elizabeth Luyster in Kentucky. She was an aunt of Capt. H. H. Luyster, of Franklin.
      Our subject was reared on the farm, and secured a limited education in the public schools. He emigrated to Kansas in the fall of 1860, and remained there until the summer of 1861, and then returned to Indiana. He enlisted in the Federal Army, in August, 1862, in Company E, of the Seventh Regiment of Indiana Infantry, as a private. At the discharge of the Seventh Regiment, in 1864, near Petersburg, Va., he was transferred to the Nineteenth Indiana Infantry, and a week later was placed in Company G, of the Twentieth Regiment of Indiana Infantry. He was mustered out of service near Washington, D.C., on May 31, 1865, having served almost three years, and passing through the battles of Antietam, Second Bull Run, Petersburgh, the Wilderness campaign, and on to Richmond, and was at the final surrender of Appomatix. [Mustered out as a corporal.]
      After the close of the war he returned to Johnson County, Ind., and purchased a farm of 136 acres, in Section No. 32; the same place was exchanged in about 1870 for another farm of 160 acres, in the same section, on the Martinsville road.
      In 1876, he removed to Florida and remained there for two years, and then returned to Johnson County, settling on his old farm.
      On September 6, 1887, he swapped farms with E. O. and J. W. Peggs, and removed to his present farm, near Franklin, which embraces 147 acres, more or less, upon which he has a substantial brick residence.
      He is a member of the Shiloh Presbyterian Church, and of Wadsworth Post, No. 127, G.A.R. In politics, he is a republican.
      He was married on October 30, 1868, to Margaret J. Graham, who was born in Johnson County, Ind., on September 3, 1845, and was the daughter of James H. Graham. She died May 11, 1878, leaving one son, Arthur G., who was born June 22, 1871.
      Mr. Hamilton was married again on January 31, 1882, to Sallie C. Covert, who was born in Johnson County, Ind., on December 16, 1850, and is the daughter of John R. Covert [& Margaret Banta]. To this union one daughter, Roxy C., was born December 23, 1882. Mrs. Hamilton is a member of the Shiloh Presbyterian Church, and her husband is an elder of the same church.