Antoinette Cook @ The News Center : Katherine Jackson, left, with Blanket, Prince and Paris.

Family matriarch Katherine Jackson is steamed at her son Randy for leading an apparently failed coup to overturn The King of Pop's will, according to published reports today.

Michael Jackson's mom has only recently figured out that Randy had aggressively sought to invalidate The Gloved One's will that generously cares for his kids and mom -- and virtually no one else, RadarOnline reported.

"Katherine was completely unaware that Randy had orchestrated his siblings signing a letter sent to the executors of Michael Jackson's estate demanding their immediate resignation," a source close to the family.

"Now that Katherine has been home for a few days, she recognizes that Randy was the one that planned this, and she is absolutely furious for him doing so."

While Katherine is willing to read Randy The Riot Act behind closed doors, she'll apparently resist any temptation to throw him under the bus publicly.

"Katherine will never speak out publicly against her children, it's just not who she is," Radar's source said.

"Behind the scenes, however, Katherine is extremely upset and disappointed in Randy's actions that have brought so much unwanted chaos into all of their lives," a source close to the situation tells us."

Katherine Jackson, named legal guardian for MJ's three kids in his will, suddenly vanished for 12 days earlier this month.

Brothers Randy and Jermaine both said their mom was resting in Arizona under doctors orders. But MJ's kids Paris and Prince both said their guardian was missing, leading to a stunning court action.

A Los Angeles judge appointed TJ Jackson, Tito's 32-year-old son, temporary guardianship of the kids.

Katherine's oddly-timed spa vacation came as Randy and Jermaine launched an effort to have their brother's will thrown out and executors of his estate removed.

They claim the document is a fraud, but Katherine and the kids -- well cared for, under MJ's will -- like the status quo.

Katherine's lawyer said his 82-year-old client and TJ Jackson have agreed to a joint custody arrangement.