Johann Wilhelm, count of Jülich & Cleves - Three wives but no children?

Well Ancestry.com said that Johann and Anna VanAldekerk had a son born 1585 died 1642 named Herman OpGraeff.

You mean the "unprooven" son: Bishop Hermann Isaac op den Graeff (as written in his about section) du to the fact that the records were delete?
From the about section of Johann Whilhelm":
John William of La March was the son of William V of Cleves (1516-1592) and Mary of Habsburg (1530-1584). Excommunicated and records *wiped* out by Church because they became Protestant believers.

I know this is controversial, but after extensive comparison between my family tree, the alleged family tree of Op Den Graeff, and my own analysis of my DNA results with GEDmatch, I’m left with no other conclusion than this was his father.