Hello Laura-

I'm afraid I can't help you as far as Homer & Rhoda Preson's relatives, but if I am on the right track here, you might want to focus your search on Los Angeles, CA.

I found a short obit for a Homer M. Preston in a Chicago newspaper dated 18 Oct 1964:

Homer M. Preston, 62, Former Chicago business man who moved to Los Angeles in 1941 and became prominent in Republican politics there as founder of Republican Associates, a group of politicallyminded business men; in Los Angeles.

Assuming this is the Homer M. Preston you seek, I did a bit of further checking...

The SSDI indicates this Homer Preston was b. 7 June 1902 and d. 18 Oct 1964.

As indicated in the Chicago obit, Mr. Preston was politically active in Republican politics when he went to California in 1941 and, indeed, is listed as a Republican delegate from Los Angeles at the 1960 Republican National Convention.

Although it does appears that both Homer and Rhoda were probably originally from Chicago and, therefore, probably still have relatives in Illinois, I think you are more likely to find their direct descendants in California.

Hope there is something here that will help you in your search.
Paul