Nick Carter sobs during tribute to Aaron during Backstreet Boys concert

Nick Carter sobbed while honoring his late brother, Aaron Carter, during Sunday's Backstreet Boys concert.

Midway through the group's show in London, Kevin Richardson got serious talking about Aaron's sudden death on Saturday at age 34. He said during the group's 29 years together, they had experienced "highs and lows" and currently had "heavy hearts" after losing "one of our family members," Nick's "little brother." He was their little brother too, they said, as Aaron launched his solo singing career in the '90s — at age 9 — opening for the boy band.

While Richardson spoke of their plan to recognize the "I Want Candy" and "Aaron's Party (Come Get It)" singer during the show, the other band members — AJ McLean, Howie Dorough and Brian Littrell — hugged Nick, who was openly sobbing on the stage. They went on to sing their hit "No Place," which is about family. Photos of Aaron and Nick flashed on the screen during the emotional performance.

Some of the photos were used in the social media tribute Nick posted after Aaron was found dead in his L.A. home on Saturday morning. Nick, who was estranged from his sibling, reflected in his post about their "complicated relationship" due to Aaron's addiction and mental illness. Through the years, Aaron revealed he had been diagnosed with schizophrenia, multiple personality disorder an anxiety, and he had addictions to prescription drugs and huffing. In a final interview, Aaron claimed he was 5 years sober, but smoked marijuana and took Xanax "legally."

Angel Carter Conrad, Aaron's twin sister, also posted a tribute to him with old photos of them as babies and toddlers.

"To my twin… I loved you beyond measure," she wrote to her sibling, from whom she was also estranged. "You will be missed dearly. My funny, sweet Aaron, I have so many memories of you and I, and I promise to cherish them. I know you’re at peace now. I will carry you with me until the day I die and get to see you again."

Aaron's on-again/off-again fiancée Melanie Martin, with whom he shared son Prince, has also posted videos. One of her crying while driving. Another was a throwback of Aaron playfully dancing. She captioned it, "Forever posting." She told the Associated Press in a statement, "We are still in the process of accepting this unfortunate reality. Your thoughts and prayers are greatly appreciated."

Among other poignant tributes was one from Aaron's teen love, Hilary Duff.

On Saturday, Aaron's housekeeper frantically called 911 at 10:58 a.m. after reportedly finding him unresponsive in the bathtub of his Lancaster, Calif., home, which had been on the market. Deputies reportedly asked for Narcan on the dispatch tape, according to Extra.

Carter was pronounced dead on the scene at 11:14 a.m. with the cause of death remaining undetermined following an autopsy on Sunday. Additional tests and studies have been requested, per Deadline.

Aaron was an undeniable teen heartthrob with his chart-topping songs and pop star good looks. However, things have long been spiraling for the House of Carters star who also appeared on Dancing With the Stars, in the Broadway musical Seussical and Off Broadway revival of The Fantasticks. He's had many arrests and turbulent relationships amid his personal struggles and also dealt with bankruptcy and debt.

In September, he entered voluntarily entered a rehab program — his fifth time — after Martin's mother took custody of his son Prince. However, he later said he hadn't relapsed, but just wanted his son back after a fight with Martin. Just two weeks later, police did a welfare check after it was reported he had been huffing during an Instagram Live, but authorities said he was OK.

In the days before Aaron's death, there was general concern about his well-being, according to TMZ. He had been pulled over on suspicion of DUI just three days before, but had been cleared. Aaron was big on doing hours long Instagram Lives and a cryptical clip from one of his final ones has been circulating in which he claimed that Martin, with whom he had been hot and cold since they started dating in 2020, told him he was "going to die."