Oh, my...the story thickens! I saw the census that shows George as the "adopted son" on the census record in Jim Wells. What he could have done to shame himself to no longer deserve the Parra name is a mystery. Why would that happen? Some ideas are he went against his religion, he got someone pregnant, he told a family secret, he became involved in a relationship that crossed racial boundaries Mr. & Mrs. Parra did not approve, he did something wrong in the military or he got in trouble with the law. What else could it be? We will probably never know.
The only facts are the birth certificate (which you must try to find) and what the death certificate says. Plus the adoption process papers in Jim Wells. These, I think, are absolutely the only facts you will ever find to solve even part of this mystery.
Now you must plan your trip to Jim Wells (or the courthouse if you already live there). When will you go?