My sister has had trouble taking care of herself, let alone her children, for the last four years. I have been able to help financially and by taking her children into my home whenever they need me too. The girls are eight and eleven and have spent almost all of their holidays, summers, and sometimes have lived with me outright. The situation has worked well, and as far as we are concerned will continue to work. Our only main concern is that the father may turn up one day and demand custody of them. He has always known where they are and yet has rarely visited them. The youngest has only met him once that she can remember. My sister is thinking about taking a temporary job in another state, but we are concerned that he may hear of this and decide to seek custody. Is there any form of guardianship that would make it harder for him to take them from my home?