Seattle's Jen Graves has a fascinating story on what happens when artists' works and ideas begin to look just a little too mcuh like other artists' earlier works and ideas.
Read the story about "Gray Area - Why Does Some Work by Lead Pencil Studio Look So Much Like Work by Other Artists?"
Then read this and then read this and tell me if "remarkable confluence" is not the category for all of these look-a-like works.
Artist "A" circa 1999-2000
Artist "B" circa 2005-2006