▶ Watch Video: Passage: In memoriam

Nick Carter, of the 90s pop music group Backstreet Boys, spoke publicly about the death of his younger brother, Aaron Carter, for the first time on Sunday.

Captioning an Instagram post with photographs that appear to show the siblings together as children and adolescents, Nick Carter said that his “heart is broken” and cited his brother’s struggles with mental illness and addiction, which Aaron Carter discussed openly during his life, as “the real villain here.”

“Even though my brother and I have had a complicated relationship, my love for him has never ever faded,” he wrote. “I have always held on to the hope that he would somehow, someday want to walk a healthy path and eventually find the help that he so desperately needed.”

“Sometimes we want to blame someone or something for a loss, but the truth is that addiction and mental illness is the real villain here,” the message continued. “I will miss my brother more than anyone will ever know. I love you Chizz. Now you can finally have the peace you could never find here on earth….I love you baby brother.”

Nick Carter and Aaron Carter seated in the audience during the 2000 Billboard Music Awards in Las Vegas, Nevada.

Kevin Winter/Getty Images

Aaron Carter had spoken candidly about his ongoing struggles with substance abuse and mental illness during a number of interviews in recent years. In 2019, Nick Carter said that along with Aaron’s twin sister, Angel, he had filed for a restraining order against their brother due to “Aaron’s increasingly alarming behavior.” Nick said Aaron confessed to having violent thoughts about Nick’s wife. Aaron Carter denied those allegations at the time.

Others, including Angel Carter and Hillary Duff, the singer and actor who dated Aaron Carter when both stars were teenagers, have shared tributes on Instagram since his death.

“For Aaron- I’m deeply sorry that life was so hard for you and that you had to struggle in-front of the whole world,” wrote Duff. “You had a charm that was absolutely effervescent…boy did my teenage self love you deeply.”

Echoing Nick Carter’s message, Angel Carter wrote, “To my twin… I loved you beyond measure. 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 Carter, whose debut album “Aaron’s Party” included hits like “I Want Candy” that brought the singer fleeting but memorable fame during the early 2000s, was found dead on Saturday. He was 34.

“We are extremely saddened and shocked to confirm the passing of Aaron Carter today,” said Roger Paul, Aaron Carter’s manager, in a statement to CBS News. “At the moment his cause of death is being investigated. We ask that you give the family time and they will have more information when available. We cannot express the outpouring of love coming in.”

Aaron Carter was found dead at a home in Lancaster, California, after a sitter said she discovered an unresponsive man in a bathtub, the Los Angeles County Sheriff’s Department said in a news release. Deputies and L.A. County Fire Department paramedics pronounced him dead when they arrived at the scene, the sheriff’s department said.