The decision was made on 22 August and brought an end the latest drama to disrupt the Jackson family since the pop star's sudden death in June 2009 from an overdose of Propofol which is a powerful anaesthetic.
"It's clear to me the children have a very strong, loving relationship with TJ Jackson," said Los Angeles Superior Court judge Mitchell Beckloff.
Katherine Jackson, 82, had been the sole guardian of Prince Michael, 15, Paris, 14, and Blanket, 10, since Jackson's death.
TJ Jackson, the 34-year-old son of Michael's brother Tito, was named temporary co-guardian of the children due to Katherine's prolonged absence from her California home, during which she did not contact the kids.
Siblings abduct mother
The family matriarch was found to be resting at a spa in Arizona, though her whereabouts had been called into question by other members of the Jackson clan.
The media went on to portray the absence of Katherine Jackson as Michael's siblings abducting her. The siblings are allegedly furious that they did not inherit any of the singer's assets, which were left to his mother and children.
Katherine Jackson was reinstated as permanent guardian of the children earlier this month, but she and TJ filed a joint request to the court asking that they be allowed to serve as co-guardians of the three children.
'Mrs Jackson is a well-informed, strong woman'
Katherine's lawyer, Sandra Ribera, said her client approved of the agreement with TJ who, like many members of the Jackson family, is a musician.
"Mrs Jackson is a well-informed, strong woman who makes her own decisions and can't be influenced by anyone when it comes to these children," Rivera said in court.
Jackson's ex-doctor, Conrad Murray, was jailed for four years in November after being convicted of involuntary manslaughter over the singer's death.