from my experience an adopted family is one you have choosen or they have to consider you a member of the family if it is that you are actually one of them you celebrate the holidays birthdays etc with them as if you were actually born into the family even the not so good times your there to support them in the way you would your birth family, it is as if you were actually adopted or you adopted them I have heard of people actually makeing it l legally binding not that you have to but i have heard of that takeing place It is also known to be because of the love and careing you share with one another I hope this is the answer your looking for as i myself and what people call an adopted family and am proud to say i have had the pleasure of calling them this for 10 going on 11 years now .