Frankie Is Not Behaving!

My husband and are settling into our new home, although Frankie, are Great Dane will not adapt, I do not know what to do about it. Frankie will not accept my father and his family members, he has become very aggressive towards them. He thinks they are stangers, he does not realise they are our family members. Keep in mind, we live on my dads property. My husband and I raised Frankie in Washington State with my mother and her family, he loves them. We had always left my mother to take care of Frankie when we were to travel or just leave for the day. My problem now, I cannot leave my home for very long, I have nobody to care for Frankie, he wants to eat them. I do not know what to do, I am hostage in my home! does anybody have any ideas?
Gina