Defeated Christchurch mayoral candidate Jim Anderton, 72, has discovered he has a sibling he ne' />

He's lost an election, but gained a half-brother.

Defeated Christchurch mayoral candidate Jim Anderton, 72, has discovered he has a sibling he never knew about living in England.

And now that the veteran MP and Progressive Party leader has lost out to incumbent mayor Bob Parker, he has time to go to the UK and meet him.

Unfortunately he will be too late to meet two other half-brothers he also never knew about; they died in the 1990s.

"I haven't had time to think too much about it," Mr Anderton said.

"I have read about other people with these experiences, and I think 'gosh, that must be incredible'. But I have, to be honest, never thought it was going to happen to me."

He's not sure what he will say to the man with whom he shares a father, Liverpudlian Terry Byrne, 74.

"How's it going?" he suggests with a hearty laugh. Or "it's been a long time between drinks".

"Yeah right - more like 72 years."

Mr Anderton recently learned that his father, Matthew Byrne, had three sons before coming to New Zealand in the 1930s, where he married Mr Anderton's mother.

After Matthew Byrne died in 1944 in a train accident, Mr Anderton was adopted by his mother's new husband.

He was initially sceptical when he was emailed by Terry Byrne's son, who had read online about him and his visit to Ireland when he was Deputy Prime Minister.

Mr Anderton visited Drogheda, a town near Dublin, where he knew his father's parents had been born.

He had no success then in tracing any relatives, but told a local newspaper about his search.

Details in an early email from Liverpool did not seem to stack up.

"In public life you get people who claim they are your mother, and your aunty and uncle.

"You get used to it. In a way, it sounds bizarre, but you just know it's not true, and you just ignore it. And I kind of did just ignore it."

But the emails kept coming, and Mr Anderton's son Chris made further investigations.

It gradually became clear there was a connection between the New Zealand politician and the Liverpool man.

The details matched up and it was "irrefutable".

Photographs sent to New Zealand of Matthew Byrne as a young man left no doubt. The likeness to Mr Anderton's son Stephen was "spooky".

"One of them was so close to my son that I thought it was him," Mr Anderton said.

He has no idea if his now-deceased mother ever knew that Matthew Byrne had children from a past relationship.

Mr Anderton said it sounded like quite a large family party was being organised in Liverpool for his visit, which will be in the New Year.

He intends to retire from Parliament next year.