I may or may not be able to help you. I do have more Ketelsen information than when I made the original post. I would need more information about your Ketelsen family in order to make a connection. Please share whatever you can, with as many names dates and places as you can provide.
Also, I have started a Ketelsen mailing list on rootsweb.com. Okay, it is not very active, so far I am the only member. But please consider joining the list and posting whatever you have to the mailing list. The lists are archived, so the information remains for others to browse. You could improve your chances for success.
And after providing more information, here or elsewhere, please be patient. I looked and lookd for years before I was able to make an unexpected connection that connected my family to its German ancestors in Schleswig.