I know a little more about Robert's son George, now.
George P Mackey married a woman named Lucretia about 1884, presumably in KY.
By 1900 George and Lucretia are in Williamson County, TX. I found this about them:
The 1900 census for Williamson County, TX, Precinct 6, Taylor, shows George Mackey, born 8/1858, age 41 and married 14 years, born in KY, father born in OH, mother in Ky, wife Lucretia, born 10/1867, age 32, having given birth to 4 children and having 4 living, born in KY, parents born in Ky, daughter Gracie, born 2/1888, age 14 and born in Texas, son Robert, born 9/1887, age 13 and born in Texas, son Jessie, born 10/1888, age 11 and born in Texas, son Lois, born 4/1893. age 7 and born in Texas -enumerated 6/8/1900
I haven't found them in any 1910 census yet but by 1920 they're in Harris County, TX and I found this:
The 1920 census for Harris County, TX, Houston, Precinct 3, shows George P Mackey, age 61, born in KY, with wife, Lucretia, age 52, born in Kentucky, son Lois, age 27, born in Texas and daughter, Thelma, age 17, and born in Oklahoma. This shows George’s father to be born in Ohio and his mother to be born in Kentucky.
The 1930 Harris County, Houston township census shows L.A. Mackey, head of household, age 61, widowed, 17 at first marriage, born in Ky with both parents born in KY, David T Young, son in law, age 28, 25 at first marriage, born in TX and parents born in Ky, daughter Thelma Young, age 27, 24 at first marriage, born in OK with both parents born in KY.
The Texas Death Index 1903-2000 has a Lucretia Adeline Mackey death as March 28, 1956 Harris County, Certificate 13962.
So apparently George ended up in Texas but I don't know a lot about what happened to the kids yet.
If any of this rings a bell, let me know. :)