In response to this, they most certainly can. People can disown their children, siblings, etc.
I maintain that you are wrong, that my wife and I are family, and I am going to leave it at that without any monkey business such as equivocating you and your wife homosexuals. Good day.
I want you to know that I wasn't comparing you and your wife to homosexuals. Your marriage is a good and blessed thing.
What I was doing was pointing out that changing the meaning of a word to include something it historically hasn't isn't good, even if it gives comfort to you and your wife. The family is the basic building block of society, and provides continuity through the generations. If you can change the definition of "family" to fit your situation, then so can anyone else - and make no doubt, they are trying to desperately.