The singer, 42, wrote on Twitter that his "heart is broken" and uploaded several photos of the pair in their younger years. 

"Even though my brother and I have had a complicated relationship, my love for him has never ever faded," he posted on Sunday.

My heart is broken. Even though my brother and I have had a complicated relationship, my love for him has never ever faded. 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. pic.twitter.com/89lsEdX9f8

— Nick Carter (@nickcarter) November 6, 2022

"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."

He added that "addiction and mental illness are the real villains here", signing off the post: "I love you baby brother."

Carter, 34, was found dead in a bath at his Los Angeles home on Saturday, according to reports.

Sky News