the last record I can locate for Robert M. Jeffs (Geffs) is 1930 Census, age 56, unmarried and in the same household, a married niece, May Estep, age 24. no idea where she fits in.
I have as parents of Nelson and Robert Jeffs (Geffs)
Father- Wiley Spence Jeffs, born 1828, Indiana
Mother - Melvina Jane Hogg, born 1840, Indiana