There is a submitted obit on the Cass Co Rootsweb page. Use the search engine for ease to bring up. There is also a death record listing for Richard Decatur Greenwood which matches his information. Obit does not list parents and death record transcription does not appear to ( transcriber usually includes parents if record had it, this transcription does not have parents listed) You can check the Cass Co courthouse for an probate record. Obit states had had 16 children and it names the surviving ones in the obit.