The Berrien County Historical Assn. published a lot of indexes to records in a set of diskettes in 1997.I have not had a chance to look for the names you mention in all of the files on these disks but did find some--Williams is a fairly common name?You did not provide any specifics such as years or township which could help to narrow things somewhat?The births and marriages are voluminous.
The file with Probate records from 1831-1930 (1-11000 something) does list three files for John Williams, #2169, #2999, #4524, and one for a Frank E. Williams, #9593.
These records are available thru the Berrien Co. Historial Assn. In 1997 they were charging $10 per file for selected information.