Stella Parton announced the sad news via X Friday ... saying her wonderful brother had passed away -- adding it's never easy to lose a loved one, but she knows David is now at peace.

The Farrar Funeral Home in White Pine, Tennessee posted his obituary to their website ... confirming he passed away peacefully at home. No cause of death was included.

According to the obit, David was a bridge builder superintendent who supervised construction all over TN. Stella confirmed in one of her posts that he was a Marine ... an accomplishment also denoted on his page.

While Dolly doesn't often talk about her family, she has expressed gratitude for their continued support of her career through the years.

Just yesterday she took to Instagram to thank her family members -- past and present -- for helping her become the music legend she is ... this, on the same day her new project "Smoky Mountain DNA," a love letter to her ancestry, dropped.

David was 82.