Once a famed attorney himself, Girardi, 82, had been under a temporary conservatorship since early February, but the conservatorship was "officially granted by the court on June 9," Robert's attorney Nicholas Van Brunt told Fox News.
Late last week, the court issued the formal order for the conservatorship before issuing letters of conservatorship to Robert on Monday.
"The issuance of letters is just the natural outcome of the court granting the conservatorship on June 9, 2021," he concluded.
Reps for Girardi did not immediately respond to Fox News' request for comment.
According to court documents obtained by People magazine, the reason for the conservatorship is Girardi's "major neurocognitive disorder." He was diagnosed with Alzheimer's in March.
The June 9 ruling gave Robert control of his brother's welfare and estate.
"It's obviously a heartbreaking situation for Robert, but we agree with the court's rulings yesterday," Van Brunt told the outlet at the time.
News of the conservatorship comes as the once-famed attorney faces scandal and several lawsuits. He's been accused of embezzling on multiple occasions.
Most recently, a judge ruled that former clients that he failed to provide with their settlement can now pursue collection efforts against Jayne, 49, after a stay had previously been placed on collections from Girardi's assets.
Girardi's own conservatorship was granted by the court just weeks before pop star Britney Spears offered an explosive testimony in court regarding her own conservatorship.
In her statement, the star alleged that her father and his team had exerted power over her that left her "traumatized," which has called the morality of conservatorships – which are generally reserved for the sick and elderly – into question.