Behaviour Changes After the Arrival of a New Sibling

The arrival of a new baby in the family is a special moment, but it can bring unexpected challenges for the older child. Many parents begin to look for answers when more frequent tantrums, regressions, or difficult behaviour appear.

What changes for the older child?

For a baby or child up to 3 years old, the arrival of a sibling represents a great transformation in their world. Until then, they were the centre of attention. Suddenly, they need to share space, time, and their parents' attention.

Common behaviours during this phase

• Regressions — returning to behaviours they had already overcome, like asking to be carried more often
• More tantrums — emotions become more intense and harder to manage
• Physical behaviours — pushing or hitting as a form of expression
• Greater need for closeness — more contact, attention, and validation

Why does this happen?

In the Montessori method, all behaviour communicates something. The child is not "misbehaving" — they are trying to adapt to a new emotional reality for which they do not yet have tools.

How to support the child during this phase

Validate emotions

Use simple phrases like "I can see you are angry" or "this is hard for you".

Create predictability

Clear routines provide security and help reduce anxiety.

Avoid comparisons

Each child has their own time and their own process.

A phase that passes

With support, empathy, and consistency, the child develops essential skills such as emotional regulation, empathy, and inner security. Gradually, they begin to build a relationship with their sibling based on connection, not competition.