Kate and Gerry McCann say that their two-year-old twins, Sean and Amelie, are handling their sister’s disappearance well, and are comforted that the siblings still seek to include Madeleine in their games.

However, experts say that helping children so young to deal with trauma is extremely complex, largely because toddlers cannot understand what has happened and the usual advice to parents to be open and honest is not relevant.

A child psychologist will begin explaining this week to the twins why their four-year-old sister has been away from the family for more than three weeks, and help them to prepare for the consequences of her disappearance.

Although children of the twins’ age are too young to understand the tragedy that has engulfed their family, and they may even appear to be unaffected by the events surrounding them, their parents still need to handle the situation carefully.

“Although they are young they would still miss a member of their close family — a sister is a very big part of their world,” Pat Spungin, a child psychologist and founder of the raisingkids.co.uk advice site, said. “They would typically say things like, ‘I want Maddie now’, instead of using terms like ‘miss’. They may also become fretful or anxious. There are no rules for a situation as ghastly as this, so I would say that anything that makes everyone feel better is fine.”

It is also important that the McCanns explain to the twins that they are not responsible for the emotional maelstrom engulfing the family, Adrienne Swan, a psychotherapist at the Priory Hospital in North London, said.

Times Recommends

• Times Charity Appeal: SolarAid
• Is it Black Monday all over again for Dubai?
• Behind the scenes at the biggest deal