My German Ancestors

I have gone back as far as my 6th great grandfather Johann Michael Geiselman (August 15, 1719 in Beihingen (OA. Ludwigsburg), Württemberg, Germany - 1785 in  York, Pennsylvania). I know there is more to this line but am unable to go any further. I have heard that the Geiselman clan was started in Southern Germany by one husband and wife. I have also heard that we were Jewish but converted to Catholism before 1600. I would like to see if anybody has anymore information on this line. I also am not sure if Gelssman is a variant of Geiselman. I do know Geisel is a variant.

I have gone back as far as my 9th great grandfather Casper Keener/Kuhner (about 1660 in Palatinate Region, Germany - about 1702 in Germany).  I know there is more to this line but am unable to go any further.

Any help would be appreciated. Thank You.