Randy Jackson, brother of the late pop star Michael Jackson, has been admitted to hospital with chest pains.
Jackson, 48, was taken to Huntington Memorial Hospital in Pasadena on Tuesday, according to the Associated Press news agency.
He was in court on Monday with his family for a hearing in the case of Dr Conrad Murray.
The doctor is accused of giving Michael Jackson a lethal dose of anaesthetic but denies involuntary manslaughter.
Last week, Randy Jackson appeared on CNN programme Newsroom and said that Dr Murray should be charged with first-degree murder.
Randy Jackson recently succeeded in stopping an unapproved tribute show to his brother Michael in Rome, which had been scheduled for 25 June, the anniversary of his death.
He thanked fans on Twitter for their support in his effort to get it cancelled.
Another Twitter post stated: "I know my brother is at peace although I miss him so much. Now that he is gone, my job is to uphold his wishes and make sure justice is served."