Bobby Brown Jr, 28, was found at his home on Wednesday, the Los Angeles Police Department said.
Officers had been called to a “medical emergency”. There is no suspicion of foul play, officers said.
No cause of death was given.
Brown Jr’s brother, Landon, shared a black-and-white photo of his late sibling to Instagram, writing in the caption: “I love you forever King.”
His death follows that of his 22-year-old half-sister, Bobbi Kristina Brown, in 2015.
Bobbi Kristina was the daughter of Brown and chart-topping singer Whitney Houston. Houston and her daughter died in eerily similar circumstances three years apart.
Bobbi Kristina spent nearly six months in a coma after being found unconscious in a bathtub at her home in Georgia.
I Will Always Love You singer Houston, one of the best-selling artists ever, died aged 48 in 2012.
She accidentally drowned in a bathtub at a hotel in Beverly Hills. A coroner listed her drug use as a contributing factor to her death.
Brown and Houston had a tempestuous relationship and were married from 1992 to 2007.
As well as Bobby Jr and Bobbi Kristina, Brown has five other children. His hits include My Prerogative, Every Little Step and Rock Wit’cha.