All children will fight with their siblings at some stage. When stepchildren are involved, the likelihood of arguments goes sky-high. There's just so much more to fight about.

While a parent and new partner have steadily built up an emotional bond, children from the two families have not fallen in love with each other. The closeness demanded in a shared household comes suddenly for them and may not be welcome.

Understand your pre-teen's feelings
In stepfamilies, the stresses of ordinary family life are multiplied, especially in the early days. A new stepbrother or stepsister can be seen as an invader, especially if they move into a child's family home. Stepsiblings come together with different expectations, family habits and rules. Jealousy can erupt over issues of space, possessions, age differences and the inevitable rivalry for parents' love. Until a new way of living together develops these conflicts are almost inevitable.

A ready-made target
As your pre-teens move up into secondary school, the academic pressure increases - as does the peer pressure in the playground. Built-up tension must be released, and this often happens at home. A stepsibling - the resident enemy - is an easy target for attack in these situations.

• Splitting Up: What's On Your Pre-Teen's Mind?
• Talking About Separation With Your Pre-Teen
• More Advice On Communicating With Your Pre-Tee
• Support Organisations: Divorce & Separation