The tragic case of Anna Kepner, an 18-year-old cheerleader from Florida who died under mysterious circumstances on a Carnival cruise, has taken a new turn. The ongoing legal battle involving her stepmother and an ex-partner is shedding light on previously undisclosed details, potentially compelling her to testify against her own son.

Two weeks have now passed since Anna Kepner, who aspired to join the Navy, was found lifeless in her cabin on the Carnival Horizon cruise ship.

While authorities have yet to determine or announce the cause and manner of her death, or make any arrests, a legal dispute between the parents of her 16-year-old stepbrother has surfaced, revealing that he is considered a suspect.

Anna Kepner is remembered in a family photo alongside her father, stepmother, and siblings. According to her online obituary, her blended family consists of five boys and three girls. (Photo courtesy of Shauntel Kepner/Facebook)

Amidst the criminal investigation, Shauntel Kepner, Anna’s stepmother, has requested a judge to postpone a custody hearing with her ex-husband, Thomas Hudson, until the investigation concludes.

That dispute could put the stepmother in a legal bind, according to Donna Rotunno, a Chicago-based criminal defense lawyer and Fox News contributor. Shauntel’s Fifth Amendment defense could disappear if prosecutors offer her immunity while going after the teen.

“The mother does not have any privilege to not testify against her son,” Rotunno told “FOX & Friends” Thursday morning. “So, a court could compel her to testify, or she could be held in contempt. And if they believe the mother was involved in any way, they could give her immunity in order to get her to speak.”

Hudson accused Shauntel of alienating their two younger children from him, including the 16-year-old. Their oldest son, 18, went to live with his father after an alleged “violent altercation” involving Shauntel and Kepner’s father, Christopher Kepner.

Anna Kepner was identified by her family as the passenger who died onboard the Carnival Horizon. (Instagram/Anna Kepner)

“The [16-year-old]’s future has been put in jeopardy because of the choices made by [Shauntel],” Hudson wrote to the judge Monday.

The teen’s current whereabouts are unclear. According to the filing, he has been released from custody and is staying with an unnamed third party.

Shauntel, in a filing of her own, denied that their oldest son had been involved in any altercation with her new husband but conceded “there is an open FBI investigation involving” the 16-year-old.

Anna Kepner, 18, was found dead aboard a Carnival cruise ship on Nov. 7, during a vacation with her family. (Anna Kepner/Instagram)

A law enforcement source told Fox News Digital Wednesday that authorities have recovered surveillance video from the cruise ship showing Kepner with a “suspect” and that the FBI is reviewing hours of additional footage from the cruise before her death. Authorities also have access to records of room key swipes aboard the vessel, the source said.

The FBI’s Miami office is handling the investigation.

Nicole Parker, a former Miami-based FBI agent and Fox News contributor, used to handle maritime cases.

A still image shows 18-year-old Anna Kepner’s cryptic final TikTok post, posted eight days before she was found dead on a cruise ship. (@fl.anna18/TikTok)

“One thing that I realized as an investigator is that people think, ‘Oh, you know, if I commit a crime out at sea, no one’s ever gonna find out,’” she told “FOX & Friends” Thursday morning. “And little do they know and many times they’re shocked. It’s actually FBI’s jurisdiction.”

Before the ship returned to port, she said, the cruise line’s own security team would have secured the scene after Kepner was found dead Friday at around 11 a.m.

“Our evidence response team would be boarding that ship — in this instance, it would have been that Saturday morning and multiple interviews would be conducted,” she said. “I would be first asking for, I want all the CCTV, I want all the video surveillance footage. I also want the key-lock records, which indicate who went in and out of that ship cabin at the time that the potential crime may have occurred.”

Agents would also interview everyone in the surrounding rooms, she said.

A memorial service for Kepner is scheduled for Thursday evening in her hometown of Titusville, Florida.