Henry Samuel May b. 30 June 1914 Texas

I am researching the May family for my son-in-law.His maternal grandfather was Henry Samuel May, born 30 June 1914 in Texas and died 17 May 1988 in Port Bolivar, Galveston,Texas. I have found he and his wife, Thelma and their daughter Thelma F May living in Houston, Texas in 1940 and have traced him back to Nederland, Jefferson, Texas in 1930.In 1930 he was living in the home of a family named Rogers, listed as a boarder, and a R M May and his wife Lucille.The census says R M was Mr. Rogers son-in-law.I am thinking R M may have been Henry's brother.R M was listed as 22 yrs old and Henry was listed as 15 yrs old.My son-in-law only met his grandfather once and his Mom has passed away so we do not have any other information, other than both census' list Henry, R.M. and both parents were born in Texas.Any guidance anyone can give will be greatly appreciated.