Three children missing with their father for a year may be feeling anxious about being isolated from other family members for so long, a clinical psychologist says.

Marokopa father Thomas Phillips and his three children Jayda, Maverick, and Ember have not been seen since December 9, 2021, when they disappeared for a second time.

On this day last year they were officially reported missing a second time, after he failed to reappear in the Te Kuiti District Court in relation to their first disappearance the previous September, which had sparked an extensive search.

Police say Phillips' disappearance breached a parenting order and there was a warrant out for his arrest after he failed to appear in court.

The children are now aged six, eight and nine.

Clinical psychologist Dougal Sutherland says much of how the children could be feeling will come down to how their father was coping and what reasons he had given for their isolation.

"A lot of it is going to depend on how the father has set this time away in the bush up with the kids. We know that it's not unusual for them to do this, to go off into the bush, but the length of time is one of the key things that's different from the past."

Sutherland says it also hinges on what the children's expectations and beliefs are about why they are isolating.

"At the very least you would expect them to be curious about why they haven't seen other family members ... and why it's been so long. At worst they might be quite nervous, anxious, worried about being away from those people. They might be worried about dad's well-being, depending on how dad is," he says.

"A lot of that is going to come up to how dad has managed to talk to them about it and about what they're doing."

The children have likely spent a year without a formal school education and friends to play with.

"Children need other children around them to play with, to learn, to just be around and be kids," says Sutherland.

"That's something that the children in this family will have been missing, just that opportunity to interact with kids of their own age.

"It's a fairly isolated and insular position to be in if it's just you and your siblings and your dad, so they would ... at least be missing out on that contact with other kids and almost definitely around their education and formal learning."

When the family are found, he says reintegration to living in a community and possibly attending school will need to be a slow process.

"There's a whole lot that's happened in the world that they won't be up to speed with, and there's probably a whole lot of other social skills that they may have got rusty on.

"It might even be quite frightening and overwhelming for them to be back in the world again. So doing that gradually and slowly at their pace is probably going to be key to help integrate them back."

Police, surf life savers, locals and family mounted a wide search for the family in 2021. Photo: RNZ / Tom Kitchin.

Sutherland says the children's wellbeing is a concern.

"There's that huge question mark around what has been going on for these kids and this family. How's the dad going? How's his mental state? And those are simply unknown questions, but potentially have big impacts on the kids."

Police says they are continually following leads on the family's whereabouts, although multiple reports of sightings across the country had been followed up with no success.

They say it's possible Phillips has found shelter and is being supported by other people.

The children's family have offered $10,000 for information leading to their safe return.

Waikato West area commander Inspector Will Loughrin says they are appealing to Phillips or anyone assisting him to bring this matter to a close.

"We have to recognise that Tom and his children lived a very isolated lifestyle and had limited use of social media or mainstream forms of communication. We believe that Tom is being supported by a person or people, and this is allowing him to continue to exist without any electronic trace."

-Amy Williams/RNZ.