Hello,
I also heard the rumours from my Grandmother and her sisters that their grandfather was German. Having traced the Gephearts quite a long way back to Peter Gepheart, they were all born in London working as watermen lightermen on the River Thames. It seems likely that s Gepheart started the rumour because of the name. Of course there were no such thing as computers and rumours carried on down through the generations. As there doesn't appear to be any evidence the Gephearts have no German ancestry.
I hope this helps.
Julie