I don't think "disown" is the word you want to use here. In English, "disown" means that you refuse to acknowledge that he is your son at all, not in a legal se

I don't think "disown" is the word you want to use here. In English, "disown" means that you refuse to acknowledge that he is your son at all, not in a legal sense, but in a social sense, i.e. "I hate you so much I no longer consider you my son". I think you probably mean, "Can you declare your son as not a dependent", not "Can you disown your son" :)