At age 92, he thought he’d lived a full life.

As a former US ambassador and decorated Marine, Theodore Roosevelt Britton Jr. had traveled to 175 countries, met Queen Elizabeth II and prayed with Dr. Martin Luther King Jr.

But life still held one more twist for him — a daughter he never knew existed.

In March 2018, Long Island native Debra Biagini reached out to Britton by e-mail, saying she had taken a DNA test — and that he was an irrefutable match as her father.

“There are people I know who still can’t believe I never knew she was my daughter,” said Britton, now 94, of Atlanta, Ga., to The Post.

Biagini was equally stunned.

She said she took the DNA test on MyHeritage.com in December 2017 because she had been dreading her upcoming 60th birthday and a friend thought it would be a bit of fun. The pals decided that they would take a trip to whichever country Biagini had the most DNA from — the idea being for her to connect more with her African heritage.

Never in a million years would Biagini have imagined that it would lead her to Britton, who served as the US ambassador to Barbados and Grenada in the 1970s.

“I opened the results, and I see this name: Theodore Roosevelt Britton Jr., and then underneath, it said ‘Father,’ ” said Biagini, 61, who now lives in Rome. “It was surreal.

“I literally got up and went to the bathroom and looked at myself in the mirror like, ‘Who are you?’”

The florist, who moved to Italy 30 years ago, already had a mother and father, the man who raised her as his daughter and who she thought was her biological dad. Both parents had since passed away.

“I just sat there for a couple of seconds. And then I kept saying the name [Britton], repeating the name, and like a light bulb, I said, ‘I know this name. I’ve heard this name before,’ ” she said.

It turns out Biagini had grown up hearing her mother often talk fondly of “Ted Britton,’’ who the older woman had described as a charming and intelligent man she once worked with at Carver Federal Savings Bank on Long Island in the 1950s.

But her mother never told Biagini that the pair had had an affair and that she was the result of it.

Britton, whose wife at the time has since passed away, said Biagini’s mother never told him about their daughter, either.

Biagini immediately got on Google to search for information about her biological dad, and the articles on him were prolific. She said she also watched taped interviews of him, and she discovered they had the same walk, the same sense of humor.

Biagini said she eventually messaged him through MyHeritage, but her voicemails and e-mails over the course of about a week went unanswered.

It turns out the sprightly nonagenarian was busy dancing at a rodeo in Texas.

When he finally got her messages, he reached out to her, and after many phone calls, the pair met in Poland in September, where Britton was attending a conference.

Biagini said she initially had many questions for Britton, including whether he had known about her before.

But “when I got to meet him and I got to know him, I really couldn’t care less anymore. It was just that he’s here, he’s Dad, he loves me. That’s it,” she said.

She said they discovered there were an “unbelievable” amount of similarities between them. For example, they both love museums, adventure and history. And they hate lamb.

Still, Biagini said, she thought that she would meet Britton once and never see him again.

But it turns out that her four new brothers and sisters and one mischievous nephew had different plans.

“We want you,” her nephew Gabriel told her. “If you want us, we’re here for you.’’

Britton beams with pride at how his family has welcomed Biagini.

“Gosh, I’ve been so blessed, so blessed. Above all, to get his beautiful lady,” Britton said.

He said that at his age, “I was about to say, ‘Well, I guess that’s it.’

“But suddenly she shows up, and I can’t leave her now.”