Our eldest, a boy who hates reading, sneers at the first girl down for her more swotty tendencies; she then snipes at the sister immediately below her who plays "Miss Perfect" to show her up. The only ones who don't tend to fight are the youngest two.
This, I assume, is because they watch the others and decide that a quiet life looks more agreeable.
Noel Janis-Norton, of The New Learning Centre, studied anthropology before she had children and was fascinated to learn that in many societies sibling rivalry is unknown. "I decided to bring my children up not to fight and 90 per cent of the time I was successful," she says with her characteristic conviction.
The first rule for reducing sibling squabbles , then, is to ignore them - unless there is real danger involved. Much of the point is to attract parental attention. Shouting or trying to apportion blame will only lead to an escalation. If, however, you designate a place for fights - out of your sight - and tell them to go there whenever they start sniping, their battles lose their savour.
Yes, but how does Noel imagine she can get rid of them all together? By understanding children's feelings. "The first child is born into a world of adults and will always need more attention than a younger child, who is born into a world of children," she says.
The solution is not to be strictly fair - except about such things as biscuits - but to meet each child's individual needs. Wise parents, says Noel, prepare to avoid future rivalries when their first child is born. "If you do too much for that child, when the next one comes along and you have less time to do things for him, he will feel deprived and blame his sibling."
It is also advisable to expect certain relationships to be troublesome. Children of the same sex usually fight more intensely than those of different genders, but problems between an elder boy and a younger girl are also common.
"Girls mature earlier," says Noel, "so a sensitive and intense boy may resent a sister who can do everything better."
The key to coaxing children into more appealing behaviour is to spend time alone with each, doing something that you both enjoy. When I suggested this to my eldest daughter - and gave her the choice - she instantly stopped moaning about the "unfairness" of life. It's important, too, to praise each child's strengths and listen to what may be upsetting each child so they don't take it out on their siblings.