Randy Jackson, brother of the late king of pop, was rushed to hospital this week after experiencing chest pains.
The 48-year-old, who was taken to Huntington Memorial in Pasadena, California, was reported to have had a mild heart attack.
He was working on arrangements to mark the first anniversary of his brother's death with a service at the pop star's resting place, Forest Lawn Memorial Park.
Randy's representative has urged fans not to worry, insisting: "He's OK."
The incident is another upset for the Jackson family, who were troubled by the news that a judge ruled Dr Conrad Murray is free to continue practicing medicine while he waits for the trial over Michael's death.