I found your Albert R Stewart on the 1940 El Campo, Wharton Co TX Census as follows: Albert R (A.R.)Stewart age 39,a Postman, for US Postoffice. Minnie Ola age 30, Imogene Millred age 12 (TX birth records show she was born 21 Oct 1927. Her birthrecord shows her father as Albert Le Roy Stewart.
The 1940 Census has: "inferred lived in Ardmore,Carter Co, OK in 1935".
Oklahoma City Directory Published Date 1935 shows:
Minneola Stewart, Ardmore, Carter Co, OK, Residence year 1935, spouse Albert L. Stewart (the only explanation for that possibly that he was living someplace else at the time)
I could not find a death date for Albert or Minneola (sometimes listed as Minnie Ola. Nor did I find them on Findagrave site...but not all cemetery information is listed there until a family member puts them there or a cemetery has been listed with all the burials (usual by a person or persons giving their time to do the work).