Alan Robinson and Walter Macfarlane have been mates for 60 years but they never had an inkling that they were actually siblings until both independently investigated their family tree and did a DNA test. The men are 15 months apart in age and have known each other for decades.
"When we played for Punahou, we were both first string", Macfarlane said, in a video posted by KITV 4.
'He was the party-er, I never went to or did any partying in high school, ' Macfarlane said.
The two were both born and raised on the island and even played football together at Punahou. They initially met in the 6th grade.
The two say they shared a special bond throughout their friendship.
Walter Macfarlane never knew his father.
Mr Robinson told KHON2: 'I had a younger brother that I lost when he was 19, so I never had nieces or nephews. "I thought I'll never know my birth mother, I'll never have any nieces or nephews", Robinson told KHON2.
In a separate bid to trace his father, Mr Macfarlane turned to a family history and DNA website and carried out a test.
Daughter Cindy Macfarlane-Flores said: "So then we started digging into all the matches he started getting".
A ideal match for his X chromosome came up with the name Robi737, who he also shared other DNA with.
Marfarlane and Robinson had identical X chromosomes; the men did some research and learned they had the same biological mother, KHON 2 reported.
Here's where Robinson comes in. She said Macfarlane realized the connection because Robison's nickname was Robi and he flew 737s for Aloha Airlines.
It turns out Robinson had used the same website to find answers about his family.
"It was so amusing because you know when we played for Punahou, we were both first string and we're brothers, playing side by side", Macfarlane said. "Yeah, it was a shock, definitely", Robinson agreed.
'Yea hairy arms, that did it!' Macfarlane shouted.
They said it had been an "overwhelming experience" as they revealed the news to friends and family.