Sir John Kirwan and New Zealand's greatest mountaineer Sir Edmund Hillary

Sir John Kirwan conquered his fear of heights to travel to Nepal to learn more about his heritage. Photo / Supplied

Kiwis have long had a strong connection to Nepal.

Something to do with a humble bloke who "knocked the bastard off" more than 60 years ago.

Now one of our most famous sporting sons has discovered a family connection to the peak-cloaked land where Sir Edmund Hillary and Sherpa Tenzing Norgay conquered Everest.

Sir John Kirwan is best known for his prowess in the No. 14 All Black jersey in the 1980s, and his later work raising awareness of mental health issues.

But on TV1 show DNA Detectives he discovered the high-achieving streak runs deep in his family, with a long-lost relative revealed to be a titan in the Himalayan climbing community in the early decades of the 20th century.

Sir John travelled to Nepal to retrace his relative's footsteps - no mean feat for someone who is afraid of heights.

"The show sort of took this turn on me that I wasn't expecting. Going to Nepal and being surrounded by so much history with New Zealand was really interesting.

"And finding out my relative was a real leader in the mountaineering field and was admired by Sir Ed, and then also he had his own mental struggles ... it was just 'Oh, wow. This all makes sense'.

"Because there's this little bit of doubt in your mind about DNA testing. It's a bit weird, eh? Someone swabs your mouth and then they come back [with all this information], so I was a little bit cynical to be fair."

There were some hairy moments for the star former All Black - one at a great height - but he was proud of how he had handled the challenges that presented themselves during several days walking in the mountains.

"I was quite proud of myself because I didn't completely freak out and have an anxiety attack over it ... the whole walk was challenging because you sort of forget how connected we are in our world.

"I just really enjoyed the connection and understanding how much of a leader [my relative] was ... even Sir Ed, they spent a month walking to where we flew into.

"Just the real adventure side of what they did ... in clothes we wouldn't wear on a wet day [in New Zealand]. It makes you feel humble and understand that that is real adventure."

DNA Detectives screens Tuesday, 8.30pm, on TV1.