PORTSMOUTH, N.H. — The last time we met, Perry McKinney was living under a bridge here, a hopeless alcoholic who had beers for breakfast and vodka for lunch. His twin brother, Conrad, was convinced — with ample reason — that Perry was on the brink of death.

We had lunch in a seaside restaurant on a sun-splashed afternoon, and Conrad ordered ice teas all around. When Conrad excused himself to visit the men’s room, Perry stopped the waitress. “Gin and tonic, please,’’ he told her.

The conversation that afternoon was unforgettable because it was so real and raw, so touching and frightening. Separated at birth by just minutes, the McKinney brothers were then 56 years old, one a fit-and-trim Peabody private detective, the other wearing the uniform of the homeless — dirty dungarees and a tangled white beard and mane.

“What advice would you give me being your twin?’’ Conrad asked, his voice freighted with urgency and concern.

“Make sure you give me $20 before you leave,’’ Perry told him.

“You know what advice I would give you?’’ said Conrad softly.

“Quit drinking?’’ his brother asked.

“Yes,’’ Conrad told him. “You can change. Do you think some day that you’ll stop drinking?’’

“No,’’ Perry told him.

That was August 1998, and Perry McKinney was true to his word. He kept drinking. His brother kept worrying and wondering how their DNA could be so similar and their lifestyles so different.

“The police would call and say, ‘Your brother’s in here, do you want to come and get him?’ And I would tell them, ‘No, I don’t,’?’’ Conrad recalled. “He used to say he was happy. I used to tell him, ‘You can do it without drinking.’ He couldn’t understand why I wasn’t an alcoholic.’’

They were born in January 1942, the first children of an alcoholic mother and distant relatives to the blue-blooded Lowells of Boston. Their occasional baby-sitter was the sister of Alan Shepard, their Derry neighbor who would later become the first American in outer space.

Both brothers quit Portsmouth High School, and their paths began to diverge. Perry was a wheeler-dealer, accumulating rental properties in Maine and New Hampshire. He married a woman he’d met in junior high school and quickly had four sons. When his wife, Sherry, died at age 29 from an aneurysm, Perry unraveled. He wandered and drank, while Conrad put down roots and built a family.

“I liked drinking,’’ Perry said recently. “I wouldn’t do it unless I liked it. I worked out every day. I figured everything would be OK. But, obviously, it wasn’t.’’

There were pledges to quit and an extended stint in rehab. Nothing worked. Until he woke up one day to find a hole in his kitchen wall. He blamed his brother. But he knew. He’d been responsible.

“To this day, I do not remember doing it,’’ Perry said. “I could have been behind the wheel of a car and hit a carload of kids. It scared me. And I said, ‘I’m not going to do it anymore.’?’’

That was 8 years, 3 months, and 15 days ago.

“It’s like having my twin back again,’’ Conrad said, who, like his brother, is a martial arts enthusiast and in terrific shape.

“I figure I’ve got another 25 years,’’ Conrad said.

“I’ve got one day at a time,’’ his brother, smiling broadly, told him.

I returned to Portsmouth on Monday and sat again with the 74-year-old McKinney brothers.

Perry, fresh from a 12-step recovery meeting, handed me a copy of the thin, paperback memoir he’s just published. It’s called “Enjoy the Journey.’’

We raised cups of coffee and sweating glasses of iced tea to hail his achievement.

It was a toast not so much to mark the book’s publication, but to what the author overcame to breathe life into his story, to him surviving to chronicle it.

Conrad smiled as Perry said his days now revolve around the simplest things.

Daily exercise. Salty air stirred by a summer wind. The sweet smell of flowers under a sparkling morning sunshine.

Who wouldn’t toast to that?

Thomas Farragher is a Globe columnist. He can be reached at thomas.farragher@globe.com.