Neurotic Terror

My fiancé, my sister, and myself all geocache. And I noticed awhile back that I can share to facebook. I have been trying to do it with no success. It keeps saying that I can't have more than one account linked to an email. I know my facebook login email is different than my geocaching.com login. Does anyone know if that's what is causing my problem. I am at a loss. We LOVE to do it, but you know, there will always be a litte edge of competition!!