The parents of your grandma Irene (Ruby Irene) were Robert Smith and Versie Moore.
According to the following death record your grandma was born on 12 Nov 1937 in KY and died on 18 Oct 1992 in OH:
There is an obituary for your grandma in "The Cincinnati Enquirer", 22 Oct 1992, Page 14:
There is a clip of the obituary of a McCAGAR, at the left hand side there is one of HAINES Agnes, in this column, please scroll down till you find the obituary of JUSTICE Ruby Irene. They are alphabetically sorted.
According to the obituary, she was the mother of Aprill Ball, Sandy Wilkinson, Robert, Daniel and Michael Justice, your father.
She was also the sister of Ethel Roberts, Georgia Grubbs, Pauline Albertson and Christine Hubbard.
Ethel Smith married Hoyt Roberts on 14 May 1950 in Cincinnati, OH. Ethel was 16 (b. ab. 1934), she was born in KY according to the following image of the marriage record:
Ethel was the daughter of Robert Smith and Versie Moore.
The following US Census record closes the circle. There is Robert Smith, his Wife Versie and their daughters Ethel (5) and Irene (2) living in KY on 1940: