Once, when he was in high school, Doug Davidson attended a basketball game and overheard a classmate comment that the opposing team had three black players.

Davidson, who was born without sight, considered this for a moment.

"Well," he said, finally. "What color are we?"

It's a story Davidson's parents Ken and Margaret tell with obvious affection, part of an archive of memories that helps define the family's values and beliefs.

In a literal sense, because Davidson, who also suffers from Type I diabetes, cannot perceive light, the terms "black" and "white" are mere abstractions. In a larger sense, his inability to make such distinctions is perfectly in tune with the family's shared belief that people should be judged on their own merits, regardless of color, beliefs or — particularly significant in Davidson's case — abilities and disabilities.

It's a belief that allowed the 50-year-old Davidson — once labeled an "idiot" by a misguided child psychiatrist — to exceed the expectations of those who believe that blind people need to be sheltered from the rest of world. And it's a belief that allows his parents Ken and Margaret — both in their 80s — to defy similar expectations of the aged.

Consider the spectacle of Davidson crossing the finish line of the 2005 Honolulu Marathon with Ken, 85, and Margaret, 81, by his side.

Or the 11 Great Aloha Runs the three have completed together.

Or the everyday routine of Doug swimming back and forth in the lagoons near the Davidson's summer home in Ko Olina, with his father calling out "left" or "right" from the banks.

"Just so he doesn't swim off to Maui," Ken Davidson quips.

And while these big and small accomplishments may seem unremarkable today, they corresponded to the conventions of the 1950s and '60s, when Doug was growing up.

Ken Davidson once spoke with a director from the Braille Institute, who told him of mental hospitals occupied by patients whose only defect was a lack of sight.

"It infuriated me to think that people would do that to their own family members," Davidson said.

"Some blind or disabled people are raised to be isolated from the rest of the world," he said. "We've never done that."

LIKE ANYBODY ELSE

It was Margaret who decided early on that her son would be raised on the same terms as the sighted world. And, she paid no more attention to the psychologist who claimed her son had a 168 IQ than she did to the one who had declared him an idiot.

"I never cared about numbers," she says "unless they prevented us from doing what we wanted. A lot of people want to put other people into one group — blind people in one group, deaf people in one group — but we didn't think he should be treated any differently than anyone else."

And so Doug grew up following the example of his two older brothers Don and Dan.

At the movies, they sat side by side drinking orange juice and eating popcorn as Doug listened to the soundtrack. When his brothers finished their piano lessons, Doug would ease his way onto the seat and teach himself the connection between touch and sound on the keyboard, eventually becoming an accomplished pianist and singer. (He once joined Don Ho on stage to sing "Pearly Shells" at a nightclub in Waikiki.)

In high school, Davidson not only made the football team but was a second-team all-league onsides kicker.

"I just practiced, practiced, practiced," Doug says. "And, like they say, practice makes perfect."

Margaret Davidson pushed her son to learn how to walk with a cane so he could travel independently. After years of struggle, she realized his resistance didn't come from fear or obstinacy. He preferred to hold on to someone's arm because it allowed him to walk, talk and maintain a human connection.

The family first came to Hawai'i in 1966. They spent eight years in Hilo before moving to a condominium at Ko Olina, where they spend six months a year renewing what Margaret Davidson calls an ongoing love affair with the Islands.

"When you die," Ken Davidson says, "you'll come through Hawai'i because it's the jumping off point to Heaven."

LIVING WITH DIABETES

Davidson said he does not consider his blindness to be a disability; his diabetes has been a more daunting obstacle. He checks his blood sugar level seven times and receives four insulin injections each day.

He also has to carefully control his physical exertion. Once, after a 1-hour swim, he fell into a diabetic coma. It took emergency treatment and four anxious hours for him to regain consciousness.

Davidson also has to be mindful of his feet, which are vulnerable to infection due to his diabetes. Although fit enough to run, he opts to walk most of his road races to avoid blisters.

Ken Davidson, a businessman and former owner of the Oakland Oaks basketball team, didn't start running until he was 55, but he hasn't stopped since. He did his first Great Aloha Run 15 years ago and it wasn't long after that Doug decided he'd like to try it, as well. For the past 11 years, they've walked, jogged and ran the 8.15-mile event arm in arm.

In 2005, Davidson again decided to follow his parents' lead by joining them for the Honolulu Marathon. They trained diligently for months and showed up on race day equipped with a bag full of groceries to maintain Davidson's blood sugar and Vaseline to keep his feet from blistering.

"I was a little concerned about my mom and dad at the end," Davidson said. "If any of us quit we all would have quit. I just told them to keep going. I had no doubt we could make it.

"When we got to the finish line it was like a breath of fresh air," he says. "It was like the apostle Paul who fought the good fight and kept the faith in Jesus. I enjoyed it all so much."

The family completed the marathon in 9 1/2 hours. They'd like to try it again if they can.

"I'm 85 years old," Ken Davidson says, laughing. "I don't know if I'll still be around. I'm already living on borrowed time."

In the meantime, the Davidsons will continue to spend their winter months in Hawai'i and their spring and summer in California, closer to Davidson's two brothers and their families. And they will continue to jog and swim and tweak society's expectations of what they should and shouldn't be doing.

"People sometimes ask us why we do all of these things," Ken Davidson says. "I tell them it's to prove that insanity runs in the family."

Reach Michael Tsai at mtsai@honoluluadvertiser.com.