The good news is you don't always have to intervene as most squabbles blow over. Rather than sorting them out, establish the ground rules: "No hitting, no insults. Stick to the issue."
But John warns play fighting is fun only if it is fun for everyone. If one child is enjoying it and the other isn't, it's recreational assault and parents need to stop the behaviour.
Parents also need to be aware that sibling rivalry can really be about their children fighting over them.
"They want you to intervene in the situation and prove your love for them, preferably by annihilating their brother," says John. "The most powerful ways to inflame sibling rivalry are, firstly, any hint of favouritism and, secondly, by allowing sibling rivalry to work and that is by giving a child the message that by fighting they have gained some victory over their sibling."
Ensure praise for one child is not used as a criticism of another ("Why can't you be like your brother?") because it will crush egos. It also locks kids into roles: if you consistently identify a child as being naughty or lazy, it will become a self-fulfilling prophecy.
You can love each of your children differently, but not one more than another. Few things are as toxic to a child's heart, or more likely to fuel rivalry, than believing parents have favourites.
John says sibling rivalry is particularly acute between "steps" in blended families and is often a major pressure on new relationships: marriages get pushed apart because of the stress of sibling rivalry.
Although it is near on impossible to give every child equal time, parents can assure each child they will get enough time. Planned "Mum dates" and "Dad dates" reduce sibling rivalry immensely.
Sometimes sibling rivalry simmers away as resentment and surfaces in "passive aggressive" behaviour to punish their sibling or parent for what they see as favouritism or unfairness. The child might be stubborn, withdraw from engaging with the family or just put a drag on family life by their negative energy. The "offender" is probably not aware they are doing it or deny it. Rather, use your insight to work on harmony.
When it comes to squabbling siblings, one of the best techniques is to separate them in different rooms. Or, as John suggests, a nine-seater van can be handy. "Put each child in a different corner, out of reach of each other, and enjoy the drive in peace." Or arrange play dates at friends' homes so siblings have time apart.
The key to coping is having rules to limit aggressive, unpleasant behaviour. Boundaries won't fix the underlying rivalry, but it does mean that the siblings know hitting, abuse or damaging property is forbidden, and it prevents the rivalry escalating.
And there is an upside to what can feel like never-ending bickering ... it helps them build resilience and interpersonal skills for later in life.
Why siblings fight?
1. If children believe they are not getting their needs met, they will do something about it - nagging, whining, demanding behaviour etc. If they believe that their siblings are rivals for the things they want, they will campaign against them.
2. Even though they may seem to be fighting over toys or treats, what they could be fighting over is you. They want you to intervene and prove your love for them by deciding the squabble in their favour. Evidence? You pick your kids up from a friend's house and she says "They were little angels". Why? Because you were not there.
3. Maybe they just don't like each other, and maybe they never will. Nevertheless, they can still learn to get on with each other and, who knows, they may grow closer as they mature.
* More information: Siblings Without Rivalry by Adele Faber, Elaine Mazlish.
