You don't give us any dates for your ancestors. I presume you know in which counties these people lived in Missouri and in Illinois. First, of course, you look for marriage records, many of them having been indexed and filmed by the Family History Library, Salt Lake City. The 1880 census and some subsequent ones are helpful in telling where the parents of each enumerated person were born, which sometimes give you excellent leads. Second, if you know in which counties these persons lived, try to find an OLD county history for each county (and surrounding counties). Some of the folks just loved to talk--and frequently (not always) they gave some pretty accurate info to the compiler of the county history--how many times they had been married, what the name of each wife was, etc., etc. The Family History Library at Salt Lake City has filmed many of these old county histories (catalog is at www.familysearch.org--link is on lower left). If you don't find one there, you might find one at the Allen County Public Library in Fort Wayne, IN. Failing either of these techiniques, I suggest you study a good how-to book on genealogy. Sometimes we overlook the obvious--such as land records, tax records, probate records, and court records. Good luck! E.W.Wallace