At the risk of repeating things you already know: If one looks at the Walters children in the 1920 census-indexed as "Waters" and campare with who is in the home in 1930,the only daughter "missing" in 1930 is Sallie May-so possibly Lonnie's mom? Then of course,in 1940,indexed as "Watters",Lonnie still resides with grandparents. You might try the Houston Public Library-under the "services" tab,"ask a librarian"; there is a research request form for obits. Can't hurt to try. It's wildly frustrating that every database that might help you on famiysearch.org is as yet incomplete-including the TX death certificates for 1986; although, your local FHC MIGHT be able to help with those in records they hold, as opposed to what they've placed online at the moment? It can be pricy, but purchasing his application for a SS# may also give you his parents names, but that is of course, not always a certain thing.