Nick Carter is speaking out for the first time about the loss of his sister, Bobbie Jean ... something he thinks he'll never fully process.
The singer broke his silence Thursday on social media, saying, "It may take a lifetime to fully process the loss my family has endured over the years – most recently, with the sudden passing of our sister Bobbie Jean. I am completely heartbroken."
He goes on to thank everyone for their "love and kind words" ... adding, "We are reminded again that life is precious, fleeting and to cherish the time we have with the ones we love. I know she is finally at peace with God."
TMZ broke the story, Bobbie and Nick's mom, Jane, told us about the "sudden death" of her daughter last month -- asking for "a prayer for my precious eight-year-old granddaughter Bella, who previously lost her father and is now also left without her mother."
Remember, Bobbie Jean was found unresponsive in her Tampa, FL bathroom ... deputies learned she was on probation for cocaine possession, but her roommates said she had not used narcotics since being released from prison.
No drugs were found in her bedroom or bathroom, and there were no signs of foul play.
As you know, their brother Aaron was also found in his bathroom in 2022 after drowning in his bathtub. His autopsy revealed he became incapacitated due to the effects of pills and huffing before drowning.