I have, on many occasions, brought my step son's son, who lives with my wife and I in Thailand, to Australia to visit with his dad. Most times I have his dad sign a letter, plus a signed copy of his passport, giving his permission for this to occur. Only one time have I ever needed to use the letter. Just today, armed with the letter, my grandson, now 11 years old, took it into his head to go through the automatic check-in by himself. Nobody stopped him. I questioned the immigration officer present who replied that if the boy is tall enough then that's OK. TIT