My Brother is Gay. .

How can I help my brother and dad have a better relationship?  My brother told my family last summer that he was gay.  I am fine with it, my mother and little brother have supported him, but my father is really unsure and hasn't really spoken to him and I'm worried, espeically since the two of them ARE IN BUSINESS TOGETHER.  How can I help mend the fence between them.  There are no fights, just silence.  My dad talks to me and says he just doesn't really BELIEVE it.  What can I do to help him understand?