The Salt Lake Tribune generally doesn't name victims of sexual abuse, but in this case, Thomson said the sisters Desirae, 32, Deondra, 30, and Melody, 26 consented to the release of their identities.
Prosecutors gave no indication of Brown's alleged victims in charges filed last week in Utah's 4th District Court. Brown, 55, is charged with one count of first-degree felony sodomy upon a child and two counts of second-degree felony sexual abuse of a child.
The charges indicate Brown engaged in sexual conduct with a child under the age of 14 between November 1990 and October 1992. Brown also sexually abused a child between March 1997 and March 1998, according to the charges.
A source close to the family told The Tribune the sisters called police after recently learning their father, who managed the quintet until 2008, planned to once again manage child musicians.
Paul Pollei, a piano professor emeritus from BYU, was surprised by the charges. He didn't teach the Brown children, but he watched them grow up at musical competitions as the first piano quintet.
"It did come as a shock," Pollei said Wednesday. "It always seemed like it was such a unified family."
News of the charges came earlier this week following a single-car car crash involving Brown and his wife, Lisa.
The couple were hospitalized after the Porsche that Brown was driving plummeted 300 feet down a Little Cottonwood Canyon embankment and into a creek Monday night. Police have said Brown, who was driving his wife back from a Valentine's Day dinner at Snowbird Ski and Summer Resort, was driving too fast for the area.
On Wednesday night, Brown and his wife remained in serious condition. Brown is scheduled for an initial court appearance Thursday.
Thomson said the Brown sisters are cooperating with local police and the Utah County Prosecutor's Office. They won't comment on the pending case, he said.
The 5 Browns don't anticipate changes to their tour schedule, according to Thomson. The group is set to perform in Logan on Feb. 28 and March 1.
"One of the greatest sources of joy and satisfaction in each of their lives is the opportunity to share their favorite music together and with fellow music lovers throughout the world," Thomson said in the statement.
The statement also sent a message to the group's fans: "The 5 Browns wish to thank their friends and supporters for their concern and prayers on their behalf during this trying time."
Who are the 5 Browns?
The 5 Browns piano group is made up of five siblings: Desirae, 32; Deondra, 30; Gregory, 29, Melody, 26; and Ryan, 25.
All the Brown children are accomplished pianists who attended The Juilliard School in New York and are recognized as Steinway Artists. The siblings' talents have also been featured on "The Oprah Winfrey Show," "60 Minutes" and PBS.