It occurs to me that we could be dealing with two separated lines here. There is documentation that some deGuerins settled in England and Ireland and eventually assumed the Gearing spelling. However, it is entirely conceivable that the name was well established long before the deGuerins left France. My forebears all stem from a deGrerin who came to Charleston SC c. 1690, most of whom use Geron, Gerron, Geren, Guerin, Garen, Guerrant, or one of the other variations, yet some of them have adopted the Gearing spelling. I have learned to distrust strict spelling as an indication of kinship. Too many other factors contribute to choice of spelling family names.