Susan, welcome to WikiTree.
The 1940 US Census is available on FamilySearch. It shows John L., 41 years old, and Violet A., 30yo, living in Detroit with 2 daughters. Both children were born in MI. John was born in TX and Violet in MT. John was a 1t Sgt. in the Army Infantry. They had been living in Detroit since at least April, 1935.
The Office of Veterans Affairs, National Gravesite Locator shows:
HUGHES, JOHN LEE; 1ST SGT DEML USA RET; DATE OF BIRTH: 01/13/1901; DATE OF DEATH: 08/20/1947; BURIED AT: SECTION 14 SITE 365, Arlington National Cemetery.
This gives you his birth date, which is really important, as there are lots of John Hughes born in TX. One of the ways you can find out more is to get a copy of his military records. Here is a link to information regarding access to military files. As he died before 1950, his records are open.
Here is a link to the SF180, the form necessary to request military records. Be sure to ask for a copy of the complete file, and not just his discharge papers (DD214), as you want get his enlistment papers.
From his military records, you may be able to find out when and where he enlisted and his nearest relative when he enlisted. With that, you could trace him farther back.
Another idea would be to go to your library and use Inter-library Loan to borrow a copy of the Orlando newspaper for the the of John's death. If there is an article or obit, it might contain the names of his parents.