Inside the Final Days of JFK Jr. and Wife Carolyn: They 'Didn't Know What Was Going to Happen In Their Relationship'

After John F. Kennedy Jr. wed Carolyn Bessette on Georgia’s Cumberland Island on Sept. 21, 1996, he thought the press would lose interest in his love life. After all, he would no longer be the happily shirtless bachelor whose dating life was chronicled as if he was an A-list star.

He couldn’t have been more wrong.

Nearly 20 years after the plane crash that killed John, Carolyn and her sister Lauren Bessette, a new biography by historian Steven M. Gillon, America’s Reluctant Prince, offers new insight into the complications of their young marriage.

“They were both very passionate,” says Gillon, who met John when he was a teaching assistant for a Brown University history class John attended. Their relationship turned into an 18-year friendship.

“John believed once he got married, the press would leave him alone,” Gillon continues. “He’d no longer be America’s most eligible bachelor. He’d be another married guy. And just the opposite happened.”

• For more on John F. Kennedy’s privilege and pain and for never-before-seen photos from friends, subscribe now to PEOPLE or pick up this week’s issue, on newsstands Friday.

Gillon says Carolyn, a fashion publicist who met John while she was working at Calvin Klein, “had a difficult time adjusting” to the sometimes harsh spotlight in which John was raised.

“The paparazzi treated Carolyn horribly,” Gillon says.

John, who had grown up surrounded by cameras since birth, didn’t understand how challenging it was for her and didn’t always know how to help. (He declined to hire security for them, thinking it would only increase the attention.)

The pressure strained their union.

From left: John F. Kennedy Jr. and Carolyn Bessette Kennedy in May 1999, months before they died. | Justin Ide/Getty
From left: John F. Kennedy Jr. and Carolyn Bessette Kennedy in May 1999, months before they died. | Justin Ide/Getty

Over time, John grew concerned as Carolyn grew more reclusive and often chose to stay home where she felt safe. At one point he asked close friend Sasha Chermayeff to invite her out for a drink. Chermayeff was surprised when Carolyn asked her, “How do you keep the passion in your relationship?”

According to Gillon, “Sasha was struck that they’d been married for less than year and she was already concerned about keeping the flame going.”

Their relationship was tempestuous: a lot of love but challenges too, including a caught-on-tape argument in Central Park a few months before their wedding.

Carolyn, Gillon says, “was fiercely protective of John and felt that he let people take advantage of him. She wanted him to stand up for himself.”

RELATED: JFK Jr. ‘Shouldn’t Have Gone Up’ the Night of Plane Crash That Killed Him and Carolyn Bessette, New Book Says

Known for her generosity, Carolyn loved to take staffers at John’s magazine, George, out for drinks and meals and she often showed up with spontaneous gifts for their friends.

At the same time, Gillon says, “She felt trapped. Many close friends suspected that she had been self-medicating with drugs. The media was hounding her and she couldn’t figure out how to have a career. She was uncomfortable going out.”

In the last year of his life, John also felt his world closing in. His best friend and cousin, Anthony Radziwill, was dying of cancer, his magazine needed funding and his marriage was struggling.

“The two most meaningful relationships in his life were coming to an end,” says Gillon.

Carolyn Bessette Kennedy | Evan Agostini/Getty
Carolyn Bessette Kennedy | Evan Agostini/Getty

• For more on JFK Jr.’s world and sudden death, pick up PEOPLE’s 96-page special edition John F. Kennedy: An American Life, available now on Amazon and wherever magazines are sold.

RELATED VIDEO: JFK Jr. & Carolyn Bessette’s Marriage ‘Struggles Were Much More Real Than People Realize,’ Book Says

John and Carolyn had been talking about starting a family and had looked at homes outside of Manhattan. “That was something that was very important to John. He wanted to have kids,” Gillon tells PEOPLE. “But Carolyn was not ready. She’d say ‘Your best friend is dying, the paparazzi are following us. This is not the time to start talking about having a family.’ “

The summer of ’96, Gillon says, John “told a friend that he was going to separate from Carolyn, letting her know how serious things were and that they needed to make changes.”

In his final days, as he was contemplating a run for New York governor in 2002, John worried about the stress on his wife.

He spent his last few nights before the crash at the Stanhope Hotel where he met his former girlfriend Julie Baker, with whom he had remained close. “John told her he was afraid of being alone,” says Gillon.

The future was uncertain, but it’s not clear what would have happened. At the last minute, Carolyn decided to join her husband at the wedding of his cousin Rory Kennedy, scheduled for July 17, 1999. Their plane never made it.

RELATED: Revealing the Real (and Very Complicated) John F. Kennedy Jr. 20 Years After His Death — ‘He Was Two People’

“She’s still making an effort to make things work,” says Gillon. “And John has ideas to keep George going. There’s evidence his relationship could have been saved. Right up until the time he dies, he’s fighting to turn his life around.”

The endless speculation over their marriage only increased after they were killed.

“John and Carolyn were wonderful people. They fell in love, they had a stunning, dreamlike wedding,” says Chermayeff, their friend. “I don’t know what would have come to pass had they not night died that night 20 summers ago — and no one does.”

As Gillon sees it, “One of John’s closest friends told me, ‘If anyone tells you they know what was going to happen in that relationship, they’re lying. John and Carolyn didn’t know what was going to happen in their relationship.’ “