Child Adoption: Adopting Older Children
First, we must realize that it is impossible to convince anyone of anything. If we try, we add stress to the dynamic, which only creates more division. What you can do is support and educate your extended family about child adoption. Yet in order to do this, you must have confidence in yourself and be 100 percent committed to this adoption, without needing the approval of your family.
It's possible your family's frame of reference is coming from horror stories they have seen in the media regarding adoption, so you can work lovingly to provide them will more realistic examples and more responsible education on child adoption.
Second, their resistance is coming from a place of fear for you. Such strong resistance is only an indication of how much they care for you and do not want to see you hurt. Meet them in their fear and ask them what they are afraid of. Simply listen to them and acknowledge the concern they have for you, remembering that it is not your job to convince them. As they are able to process their fears, they will be more open to you educating them on the positive aspects of child adoption.