Madeleine McCann’s four-year-old twin siblings are now slowly grasping the horror of her abduction, their parents revealed yesterday.

Sean and Amelie were just two when their big sister was snatched but Kate and Gerry have since gradually explained the grim truth to them.

It is poignantly clear the youngsters still hold Madeleine close to their hearts.

Gerry, 41, said: “They talk about her more than Kate and I do. It’s incredible.

“They don’t ask so many direct questions but as they’re getting older more of the gaps are being filled in.

“They know Madeleine’s missing, they believe she has been taken and they know it’s not right that she has been taken. They understand the person who has taken Madeleine has done something very bad.

“They have asked why she’s been taken and we said, ‘We don’t know, but obviously they wanted Madeleine’. They know it’s not right and they want her back.”

Kate, also 41, added: “We made it as light as possible for Sean and Amelie but in a way they can understand.

“We made it sound like, ‘Even if you really want something you shouldn’t take it if it belongs to someone else’.”

The kids, who now attend school, are so heartbroken at having Madeleine ripped out of their lives they have even vowed to attack the kidnapper when he is caught.

Heart specialist Gerry revealed: “They’re saying, ‘When we find who took her we will fight them’. That doesn’t come directly from us saying that.

“Amelie this week was saying, ‘When I find that man I’m going to do this and that’. I said, ‘No, we will give them to the police and then we’ll put them in jail’.”

Since Madeleine’s May 2007 abduction in Praia da Luz, Portugal, her bedroom at the family home in Rothley, Leics, has remained just as she left it.

It is a bedroom her parents fervently hope she will return to one day. Kate said: “There are lots more presents and pictures from Sean and Amelie. She’s an integral part of our life, of our home.”

Meanwhile, they have bravely striven to give the twins happy, normal childhoods and shield them from the anguish the couple endure.

But the youngsters know there are times their parents’ mask of calm slips. Kate said: “It’s difficult. I don’t want to be upset in front of them all the time.

“We have as many happy times as we can, which is what they deserve. There will be occasions when one or another of us gets upset, but that’s inevitable.

“Anything can spark that – the most innocent thing. But they know it’s OK to be sad. They know we’re sad because Madeleine’s not with us.”

She and Gerry believe the twins having each other has helped them develop into cheerful children. He said: “They’re not sad very often, and that makes life for us an awful lot easier. They have each other and I’m sure that has helped them.

“Had this just been one other younger child it would have been harder. To the casual observer it would look superficially quite normal, especially when we have the kids. We make sure they get the love and attention they deserve and Madeleine got.”

The couple refuse to give up hope that Madeleine is alive and Gerry vowed: “We’re going to do everything in our power to find her and her abductor.”

The latest step in the search saw the release of an online video this week showing how she might look aged at six.

Gerry told how the twins were aware of the efforts going on to find her.

He said: “When I think of Madeleine I think of the little girl running around the house and on holiday.

“Sean and Amelie do a brilliant job of bringing us back to reality. They see stickers or wristbands and say, ‘Oh look, that person is helping us to find Madeleine’.”

Kate admitted she was sometimes fearful about her daughter’s whereabouts and confessed: “I try to push it out of my mind because it upsets me and it doesn’t help.”

And she pleaded: “It would be fantastic for Sean and Amelie – regardless of myself and Gerry – for Madeleine to be back. We’re urging people to help us. Please don’t give up on Madeleine.”