Thanks very much for your quick replies guys. Scootergirl, my boyfriend is applying for a defacto visa and is not planning on sponsoring any of his brothers and sisters. Thats a good idea to at least just put their names and then give an explination in the additional information section.
Thanks wanderer, I will send a quick email off to immigration and just ask what they think is best. The only problem is that I never seem to get responses from this Aus Embassy in South Africa. But Ill give it a shot, otherwise Ill phone them.