The civil lawsuit, filed Wednesday against Nick Gordon in the Superior Court of Fulton County, Georgia, alleges that Gordon's behavior "caused, among other things, substantial bodily harm to Brown."
It also claims that since Brown's hospitalization in January, Gordon accessed her accounts and stole more than $11,000.
Attempts to contact Gordon for comment were unsuccessful Wednesday.
He posted a message to his Twitter account that did not mention the lawsuit, but said, in part: "We keep praying."
'Condition has continued to deteriorate'
The 22-year-old daughter of the late singer Whitney Houston was found unresponsive
at her home in January.
"Despite the great medical care at numerous facilities, Bobbi Kristina Brown's condition has continued to deteriorate. As of today, she has been moved into hospice care," read a statement from the family.
"We thank everyone for their support and prayers. She is in God's hands now."
Brown, Houston's daughter with singer Bobby Brown, was found unresponsive January 31 in a bathtub at her home in the Atlanta suburb of Roswell. The extent of her injuries was never made public.
Gordon was one of the two people who reportedly found Brown. Brown called the 25-year-old her husband, but her father's attorney said the two were never married.
A family friend has said Gordon is not welcome in Brown's hospital room, and he has not seen her since that night in January.
Bobby Brown arrived Wednesday at an Atlanta-area hospice facility, a source close to the Houston family told CNN.
Prosecutors get case
The lawsuit states that just prior to January 31, Brown told someone that Gordon was "not the man she thought he was" and set up a time to meet that person later in the day.
Brown never made it to the meeting, the suit claims.
"Instead, on the morning of January 31, 2015, Brown became embroiled in a loud argument with Defendant at her townhome. The loud argument ended and Brown was later found unresponsive and unconscious, face down in a bathtub, with her mouth swollen and another tooth knocked out," it reads.
Police have said they are treating Brown's case as a criminal investigation.
On Wednesday, Roswell Police Chief Rusty Grant told CNN that the investigation is in the hands of the Fulton County District Attorney's Office.
"Our department has completed the initial investigation. The investigative file, which is quite large, has been turned over to the Fulton County District Attorney's Office for their review, and to determine if any criminal charges are appropriate," he said.
, Brown's grandmother Cissy Houston said that
Brown had "global and irreversible brain damage."
Houston said then that Brown was no longer in a medically induced coma, but that she remained unresponsive.
When Whitney Houston died in 2012, she was also found in a bathtub. A coroner ruled her death
an accidental drowning, with heart disease and cocaine use listed as contributing factors.
Brown is Houston's only child.