They sit on opposite sides of the political tracks, come from different generations and have very different leadership styles.
That hasn't stopped Australian Prime Minister Scott Morrison and New Zealand's leader Jacinda Ardern building a strong relationship befitting the two countries' recent history and long-held values.
It's a relationship that, until now, has been sculpted in tragedy and hardship.
"The last 12 months has, if nothing else, demonstrated just how close New Zealand and Australia are," Ms Ardern said.
"Whether it's the fires in Australia, and the hundreds of personnel that have gone from New Zealand to Australia to support them and their efforts.
"Or Whakaari White Island, or coronavirus, we've had plenty of examples in the last 12 months where we have been extraordinarily close together."
Most recently, there has been collaboration during the Covid-19 crisis, with New Zealanders and Australians sharing space on each others' mercy flights from the troubled Chinese region.
Ms Ardern could have also added to her list the Christchurch mosque shootings of March 15 last year, given collaboration with Australian police and experts in the aftermath of the attack.
The pair will have plenty to reflect on when they meet in Sydney on Friday for the annual meeting of prime ministers.
"Of all of the leaders that I work with, differently, Prime Minister Morrison is the one that I speak with the most," Ms Ardern said.
"I've had officials joke that they no longer think they need to do the work themselves because we often just resolve things directly together.
"It would be fair to say actually the very things that draw communities closer together are the things that often draw countries close together as well.
"We're countries that lean on one another in times of need.
"That is an incredibly important relationship and having that ability, I think it's meant we've been able to troubleshoot things very quickly."
That doesn't eliminate the differences.
In the Pacific, New Zealand is held up as a great ally on climate issues; Australia is lambasted for worshipping fossil fuels.
The divide is such that Ms Ardern, who has enshrined into law a pathway to reach net zero carbon emissions by 2050, says she won't bother to raise the issue in Sydney.
She has pledged to discuss the "corrosive" issue of deportations, which has seen hundreds of New Zealanders - some with very few links to the country - deported from Australia after committing serious crimes.
Australia has been unrelenting in its stance, and New Zealand is realistic on whether any concessions might be made.
There will also be discussions about commerce, with Ms Ardern referring to "what we can do at our borders to make it easier for our businesses to move between each other".
In a side meeting, Indigenous Australians Minister Ken Wyatt and Maori Development Minister Nanaia Mahuta will also sign a groundbreaking collaboration agreement on indigenous issues.
Ms Ardern will also meet NSW Premier Gladys Berejiklian and Governor-General David Hurley before returning to Aotearoa on Friday night.
Australian Associated Press