"We didn't go out in public that much," Brown once said of his much-dissected romance with Ronstadt. "It was a pain in the neck"
Linda Ronstadt and Jerry Brown
From left: Linda Ronstadt and California Gov. Jerry Brown in the late '70s

"The governor and the rock queen," one magazine cover declared them — or, as PEOPLE put it in 1979, "Ronstadt & the Guv."

For a time in the '70s, there was perhaps no odder odd couple in the overlapping worlds of celebrity and politics than California Gov. Jerry Brown and Linda Ronstadt, the chart-topping country-rock star.

While the relationship was a passionate one, the biography Man of Tomorrow: The Relentless Life of Jerry Brown by Jim Newton reveals it was also in keeping with both of their norm-defying personalities.

Part of the coupling played out in the spotlight, most famously during an ill-fated trip to Africa. But much of it remained off-limits from the public, the subject of endless speculation.

"Would you marry someone you'd only known for two years?" Ronstadt, now 73, famously shot back at a reporter who had asked about marriage rumors in 1979.

"Ronstadt would quickly become part of Brown’s lore—and he of hers—in part because she was at least as well known as he was inside California, and she was certainly more famous outside the state," Newtown writes in Man of Tomorrow, which released on Tuesday and pulls from dozens of interviews with Brown, 82, and his wife Anne Gust, 62, that were conducted over the course of five years, as well as archival records.

“They really like each other,” Assemblyman Willie Brown told Newsweek in 1979, which Newton cites in the book. "He’s a different person when he’s with her. There’s a side the public never sees. He’s flirty, flippant and very funny. And he’s as interested in her physically as I’d like to be."

The biography follows Brown's surprising story — the son of a California governor himself, he studied to become a priest before entering politics and twice served as governor, with a 30-year gap in between — as it ties to the larger history of California, which emerged as one of the largest economies in the world.

Linda Ronstadt and Jerry Brown
From left: Linda Ronstadt and California Gov. Jerry Brown

Brown's romantic life proved to be just as atypical as his career. When he was in his late 30s, opponents speculated that he was gay because he was attractive but remained unmarried, Newton writes in the new biography.

Then there were the over-eager mothers who wanted to set Brown up with their daughters.

"His correspondence from early in the first term includes a number of letters in which the senders tried to set him up with dates. 'To quote an old adage: 'All Work and No Play Makes Jack a Dull Boy (or Dull Governor),' wrote one helpful correspondent," Newton writes of Brown, who was first elected governor of California in 1974. "She suggested that Brown look up her daughter, a nutritionist working in Sacramento. 'Not only is she very pretty, but she is very intelligent,' her mother added. And then he showed up with Linda Ronstadt on his arm."

The couple initially dated without much fanfare in the early '70s, but they lost their privacy when Brown was elected to lead California and Ronstadt released an album, Heart Like a Wheel, around the same time, according to the book. (Ronstadt would go on to became a 10-time Grammy winner.)

They alternated living together in their homes in Los Angeles and Malibu. "We didn’t go out in public that much," Brown told the author in 2016, per the book. "It was a pain in the neck."

"Jerry Brown and I had a lot of fun for a number of years," Ronstadt wrote in her 2013 memoir, Simple Dreams. "He was smart and funny, not interested in drinking or drugs, and lived his life carefully, with a great deal of discipline. This was different from a lot of men I knew in rock and roll. I found it a relief."

Newton explains in Man of Tomorrow that the singer "disliked politics" and tried to remain separate from that part of Brown's life.

"I don't think she wants that kind of life," Ronstadt's mother told PEOPLE in 1979.

The two could be reticent, even together. "He's a good guy," Ronstadt said during their notorious trip to Kenya that same year, "but we're not alone very much."

Linda Ronstadt and Jerry Brown

RELATED VIDEO: Watch a Clip from the Documentary Linda Ronstadt: The Sound of My Voice

Despite Ronstadt's aversion to politics, she was willing to play "unofficial First Lady" sometimes, according to Man of Tomorrow. She especially enjoyed social gatherings — and wasn't afraid to get friendly with royals.

"During a visit by Princess Margaret to Los Angeles, Brown annoyed the princess by announcing that he would not be staying for the full meal—a glaring breach of royal protocol," Newton writes. "The two were seated next to each other, and when the food was served, Ronstadt dropped by their table, putting one hand on her boyfriend’s shoulder and the other on the princess’s shoulder. Ronstadt, dressed in white miniskirt and red boots, snatched a piece of food off Brown’s plate and asked, 'What are we having to start?' The princess was horrified."

When Brown campaigned for president in 1980, his girlfriend organized two concerts in his honor. But, despite his efforts, Brown didn't win one primary and had to drop out of the race, according to the book.

After Brown's presidential campaign ended, he and Ronstadt "drifted apart," Newton writes. But their orbits never seemed to stray too far. In 1988, for example, the two had a warm run-in at one of her California concerts. When PEOPLE asked Brown to confirm he was at the show, what he'd thought and if the two were rekindling their flame, a representative said only: "Yes."

After their '70s romance, Ronstadt went on to date others — like Star Wars' George Lucas – and adopted two children, but she never married. Brown and Gust wed in 2005.

As he told PEOPLE in 1981: "I definitely want to have a wife and children. I just haven't found the right person. I'm struggling to do the work that I'm doing. And that struggle is paramount. My wife would have to be very committed to what I'm doing. Also, I have a very restless mind and that restlessness may, to some degree, be inconsistent with domesticity."

“Neither of us ever suffered under the delusion that we would like to share each other’s lives," Ronstadt wrote in her 2013 memoir. "I would have found his life too restrictive, and he would have found mine entirely chaotic. Eventually we went our separate ways and embraced things that resonated with us as different individuals … We have always remained on excellent terms."

Speaking with PEOPLE last September, Ronstadt said she and Brown were still friends after all these decades.

“He came for Christmas last year."

Man of Tomorrow by Jim Newton is on sale now.