These records from familysearch.org may indicate children of Rutha J -?siblings of Robert - maybe you can trace them - to see if you can locate parents names. One possibility is William.
https://familysearch.org
Akansas, Marriages
Name: J C Adams
Marriage 30 Sep 1894 Randolph, AR
Age 36 Birth 1858
Residence Warm Springs, Randolph, AR
Spouse Rutha Hughs
Age 30 Birth 1864
Marriage License Date 26 Sep 1894
US Census, 1910 Wiley, Randolph, AR
SELF John C Adams M 50y TN
WIFE Rutha J Adams F 47y AR
SON Sol Adams M 17y AR
SON Jesse Adams M 12y AR
U SCensus, 1900ED 98 Gatewood Township, Ripley, MO
Head John C Adams M 45 TN
Wife Rutha J Adams F 39 AR b Feb 1861 7 children, 6 living
Dau Adams F 22 TN
Dau Emma Adams F 12 AR
Son Sylvester Adams M 8 AR
Son Jesse Adams M 3 AR
Stepson James Hughs M 14 AR b May 1886
Stepdau Ethel Hughs F 11 MO b. Feb 1889
U S Census, 1880 Warm Springs, Randolph, AR
SELF William Hughes M 23 AR AL AL abt 1857
WIFE Ruthy Hughes F 17 AR AR AR abt 1863
DAU Jennie A. F. Hughes F 1 AR
BRO James Hughes M 18 AR abt 1862
U S Census, 1920 Randolph, AR
SELF Jesse Adams M 22y AR
WIFE Ella Adams F 19y AR
SON Edgar Adams M 9m AR
MOTH Ruthie Adams F 57y AR Wid
US Census, 1940 Union Township Ripley, MO
Head Edd Rush M 60 AR
Wife Lou Rush F 58 AR
Son Eddie Rush M 24 MO
Dau Mabel Holland F 31 AR
Granddau Bettie Lou Holland F 8 MO
Mothinlaw Rutha J Adams F 79
Ed Rush
Birth 1879 Ingram, Randolph, AR
Bride Lou Hughes
Birth 1881 Warm Springs, Randolph, AR
Marriage 31 Dec 1899 Randolph County, AR
Jessie Adams
Birth 1896 Walnut Ridge, Randolph, AR
Bride Name: Ella Pribble
Birth 1899 Walnut Ridge, Randolph, AR
Marriage Date: 27 May 1917