JACKSONVILLE, Fla. – A woman accused of kidnapping an hours-old infant from a Jacksonville hospital in 1998 lost a child she'd carried for nine months and had a nervous breakdown before taking the girl and raising her as her own daughter, according to a source close to Gloria Williams' family.

Williams, 51, was arrested on kidnapping charges. The girl she raised as Alexis Manigo was actually born Kamiyah Mobley. The 18-year-old met her birth parents for the first time Saturday.

The I-TEAM's source said that because Williams was pregnant and had carried the baby to term, her family had no reason to question whether Alexis was her daughter.

But now the family is learning Williams' baby was stillborn, and she's been living a lie for nearly 20 years.

Williams has two sons, and the boys' father filed for divorce from her in 1993. She later met Charles Manigo and became pregnant with her third child.

The source told the I-TEAM that Williams went into labor in the summer of 1998 when her sons were out of state visiting their father.

The source said Williams now says she was out shopping, had contractions and went to a nearby hospital, but that baby, possibly also a little girl, didn't survive.

Williams' family believes that in the throes of grief and possible postpartum depression, Williams did the unthinkable and immediately drove south and stopped at what was then University Medical Center in Jacksonville.

Police said that at the hospital, Williams befriended Kamiyah's 16-year-old mother by pretending to be a nurse and then tricked the teen into letting her leave the room with the baby. Instead, she left the hospital and wasn't found for 18 years.

The source believes Williams brought Kamiyah straight back to Colleton County, South Carolina, 200 miles from Jacksonville and passed the infant off as her daughter, Alexis.

The source doesn't believe Williams planned the kidnapping maliciously but that she just snapped.

As baby Kamiyah's abduction reached a fever pitch in Jacksonville and made international headlines, Williams' family never had a single question that the baby could be the missing child. The source said Williams acted completely normal and returned to life raising her now three children.

After news broke this week that the child they had known as Alexis was actually kidnapped baby Kamiyah, Williams' family was shocked and saddened for all of the victims -- and for Williams, who held on to the secret of the baby's identity and the loss of her child for so long without sharing it with anyone.

The source even questioned whether Williams might have blocked the truth from her own memory until investigators came calling.

“(It) hurts us to know she carried this in her heart or her head all these years and was not able to talk about it,” the source said.

The story Williams is telling her family about the stillborn baby will also be investigated as part of the kidnapping case against her.

While medical records are excluded from open records requests, investigators will have access to the information and can confirm if, in fact, Williams had a stillborn child.

Williams' two grown sons, who live out of state, returned to South Carolina to see their mother after her arrest.

They are reportedly very close with their mother and were shocked to learn the true identity of the girl they believed was their half sister.

Both they and their father, Williams' ex-husband, have declined to comment.

The source said Alexis' family wants to support any relationship she wants to have with her biological family.

Man told he was Alexis' father

Charles Manigo, who was Gloria Williams boyfriend 18 years ago, told ABC News that he was told she gave birth to the baby while he was away.

Manigo said that he and Williams raised her from the time she was a newborn, and they shared custody after they split up in 2003. He said they celebrated milestones together, like her prom.

"She was the love of my life," Manigo told ABC News.

But the teenager, who is still processing that the mother she had known is accused of kidnapping her at birth, said the man she was told was her father was not a big part of her life.

"He did nothing," she posted on Facebook. "He was the reason I didn't go to my senior prom. ... I call my granddaddy, 'Daddy,' and he earned it."