You may be right. But we're inching pretty close towards arguing by definition now. So to avoid that, let me rephrase my original response to mattnewport's question:

You're right, by most interpretations utilitarianism does weigh everybody equally. However, if that's the only thing in utilitarianism that you disagree with, and like the ethical system otherwise, then go ahead and adopt as your moral system a utilitarianism-derived one that differs from normal utilitarianism only in that you weight your family more than others. It may not be utilitarianism, but why should you care about what your moral system is called?