My son insists that he is entitled to having overflowing wine in a Kiddush cup the same as his father. I say that this would be disrespectful. I have been in homes for the Shabbat evening meals where only the father or head of family (male) has an overflowing wine Kiddush cup. I have also been in homes where everyone at the table has a Kiddush cup, but only the father or head of family has an overflowing cup. But, my son says that every male over the age of 13 should have this honor as well. What is correct?
Every cup which is used for a bracha (kidush, bircat hamazon, sheva brachot, etc) should be full if possible. It does not have to be overflowing, though there may be customs that it be done. There is a widespread custom in regards to havdalah that the cup overflows. Since it is not a halacha regarding kiddush, one cannot "demand" this "honor". Respect of parents is a Torah requirement, this custom is at best a local custom that surely should not be insisted upon if it causes any discomfort in the family.