In March, the model, 25, had a ministroke after a blood clot traveled from her heart to her brain. (Hailey later shared that she was diagnosed with a grade 5 PFO — a small opening in the heart that usually closes after birth — and underwent a procedure to correct the condition.)
Then, after postponing three dates of his highly anticipated Justice tour, the pop star, 28, revealed in a candid Instagram video on June 10 that he had been diagnosed with Ramsay Hunt syndrome, a rare neurological disorder brought on by a reactivation of the same virus that causes chicken pox and shingles. It caused paralysis on the right side of his face, leaving him unable to blink or smile.
"Hailey has been so supportive of Justin, just like he supported her with her health issues," a friend of the couple's says in this week's PEOPLE cover story. "They're unbreakable."
Dimitrios Kambouris/Getty Justin Bieber and Hailey Baldwin Bieber
"I think honestly the silver lining in what I went through, what he went through, is it really bonds you," she said.
During her appearance, Hailey also assured fans that Bieber is on the mend.
"He's going to be totally fine," she said. "This is just a really out-of-nowhere, weird situation."
Two days before Hailey's appearance, Bieber — who postponed the remainder of the U.S. leg of his Justice world tour, originally scheduled to run through July, to focus on his health — shared an update on social media, acknowledging he was facing a "horrific storm" but had already seen improvement in his condition.
"It's been rough," says a source close to Bieber. "There is nothing he can do to speed up the recovery, so he just has to be patient. He is supposed to take his medications, rest and eat nutritious food."
Characterized by acute facial weakness, ear pain, a rash around the ear or on the face and sometimes hearing loss, Ramsay Hunt syndrome affects only five in 100,000 people a year. Anyone who has had chicken pox or has never been vaccinated against chicken pox is susceptible, say experts.
"The virus, even if you had it as a child or as a young adult, stays dormant in your body until something triggers it to reactivate," says Dr. Amit Kochhar, director of the Facial Nerve Disorders Program at Providence Saint John's Health Center's Pacific Neuroscience Institute, who has not treated Bieber. "Once the nerve that causes movement of the face — lifting your eyebrow, closing your eye, smiling, things like that — becomes inflamed, you get facial paralysis."
According to Dr. Scott Stephan, director of Vanderbilt University's Facial Plastic and Reconstructive Surgery program, many patients see "significant" improvement after a few weeks of treatment, which usually includes high-dose steroids and antivirals.
"By three months most people would have significant recovery back," adds Stephan, who has not treated the singer.
Stephan also debunked social media claims that the COVID vaccine led to Bieber's condition, saying, "There's been no established link between vaccines and facial weakness."
RELATED VIDEO: Justin Bieber Shares Update on Ramsay Hunt Syndrome Recovery: 'Each Day Has Gotten Better'
Though Hailey had been traveling between her and Bieber's home in Los Angeles and New York City for the promotion of Rhode, she "constantly checked in on Justin," says the source close to Bieber. "It's been very scary for her. Even though she knows he will be fine, it's definitely been an overwhelming year so far."
The young couple first met in 2009, when a then-12-year-old Hailey was introduced to the 15-year-old pop wunderkind by her father, actor Stephen Baldwin, backstage at the Today show.
They stayed friends and dated briefly in 2015 before things ended in a "very dramatic" breakup, Hailey told Vogue. Months after rekindling their romance in 2018, they wed at a New York City courthouse and followed that with a bigger celebration in South Carolina a year later.
"I just felt like that was my calling," Bieber told GQ last year. "Just to get married and have babies and do that whole thing."
Bieber has been open about struggling with mental health issues, including depression, ADHD and anxiety.
"I realized there was some serious healing I needed to go through in order to get to a place where I could be in a healthy, serious relationship, because I had a lot of trauma and scars," he said last November on Judah and Chelsea Smith's In Good Faith podcast. "Luckily, Hailey accepted me as I was."
Through the difficult times, her support never wavered.
"I made a decision," she said in the same interview. "I know for a fact that I've loved this person for a very long time, and now would not be the time to give up on him. I just wouldn't do that to him."
Kevin Mazur/Getty Justin and Hailey Bieber
While navigating high-profile careers, the couple have worked hard to carve out a quiet life together. During the early days of pandemic shutdowns, "we really just got to be with each other and laugh and have fun," Hailey told PEOPLE in 2021. "We got to road-trip and do things that we honestly weren't going to have the time for."
They also found a haven in Bieber's hometown in Ontario, Canada.
"They are like regular people here," says a local. "Justin loves Canada and can enjoy himself here without a lot of the hassle."
Though they wed young, sources say they've grown together.
"Justin has matured in his marriage," says a music source. "Hailey has been a good influence. They will do whatever it takes to help each other."
Leaning on his faith and loved ones, Bieber is looking forward to getting back on tour in Europe later this summer.
"It's a setback, but everyone has setbacks: He's going to move forward and get healthy," says the couple's friend. "He's in good spirits and looking forward in his life and career."
For all the details on Justin Bieber's road to recovery, pick up the latest issue of PEOPLE, on newsstands everywhere Friday.