Missing New Hampshire 7-year-old Harmony Montgomery was so close with her younger biological brother in foster care that she fed him with a bottle and slept with her arm around him.

Now in a safe home, he sometimes calls out for her at night and looks for her on the playground, according to his adoptive parents. 

Manchester police opened a large-scale investigation last week after they said they discovered that the girl has not been seen since October 2019, when she was just five and her brother three.

Missing Harmony Montgomery and her little brother Jamison

Missing Harmony Montgomery and her little brother Jamison at a foster home more than two years ago. (Courtesy: Johnathon Miller)

NEW HAMPSHIRE POLICE ANNOUNCE 24/7 DETECTIVE-MANNED TIP LIEN FOR MISSING 7-YEAR-OLD HARMONY MONTGOMERY

Blair Miller, a Washington, D.C.,-based television news reporter, and his husband Johnathon Miller are the adoptive parents of Harmony’s little brother, Jamison.

"Harmony was the only thing consistent in Jamison’s life, through unification with the mom, back into foster care, Harmony is all Jamison had," Johnathon Miller told Fox News Digital Tuesday. 

They were so close in foster care that Harmony would sleep with her arm around him every night, as if he were her son, he said. 

When the Millers adopted Jamison, he only had one bag in his possession – and it held a Tickle Me Elmo toy that they later learned Harmony had given him because he had nothing else.

NEW HAMPSHIRE GIRL, 7, REPORTED MISSING 2 YEARS AFTER SHE WAS LAST SEEN

"When he came to foster care, he had no toys," Miller said. "She gave her Tickle Me Elmo to Jamison."

Once the Millers adopted Jamison, they said they heard him crying at night for his sister.

The Millers and their three adopted sons, including Jamison

The Millers and their three adopted sons, including Jamison on the left. (Courtesy: Johnathon Miller)

The siblings' closeness prompted the Millers to inquire about adopting Harmony themselves to reunite them – but by then, Massachusetts Department of Children and Families authorities told them she had already been returned to the custody of her biological father.

So the Millers instead sought to send Harmony gifts around the holidays and her birthday on behalf of her little brother – but were unable to get in touch.

They contacted her biological mom, who is also Jamison’s mother, but her efforts to connect the Millers with Montgomery were unsuccessful.

"All she thought was that Adam was keeping Harmony away from her and from Jamison because he just didn’t want them to have a relationship together," Johnathon Miller said. "She told us that she had sent an email to someone at the local government level, and that she was going to the courthouse and to the police…And then she was able to contact Adams family, and that's when they expressed concern that Harmony could be in danger."

Harmony Montgomery, 7, was reported missing last week

Harmony Montgomery, 7, was reported missing last week — two years after she was last seen. (National Center for Missing and Exploited Children)

The mother, Crystal Sorey, did not immediately respond to Fox News Digital’s requests for comment.

In a Facebook post that was visible Monday but has since been removed from view, she asked for help finding Harmony and wrote that her daughter’s dad, Adam Montgomery, was also missing.

Police did not immediately respond to questions about his whereabouts. A man who answered a phone listed for Adam Montgomery hung up after a reporter identified himself, then responded via text message saying, "This isn’t Adam."

On Monday, Manchester Police Chief Allen Aldenberg said investigators had interviewed "many, many family members" but declined to go into specifics about which ones or who was responsible for taking care of her.

The Millers also said they had no success contacting Montgomery or his new wife over social media.

Once Sorey saw the red flags, Johnathon Miller said she acted right away – raising the alarm that her biological daughter had gone missing. Police in Manchester, New Hampshire, revealed last week that the girl had not been seen since October 2019.

"This feels like a nightmare for us that our son, that our job is only to love and protect him, that we have not been able to do the same for his sister," Miller said.

Blair Miller, a Washington-based news anchor for Boston 25, told Fox Nation’s "Crime Stories w/ Nancy Grace" Tuesday that the young siblings had spent years in and out of foster homes.

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"The stories we’ve been told by their foster parents is that Harmony looked after Jamison," he said. "And the two had this bond, and Jamison is aware of that bond."

The bond was so strong Johnathon said, that when Jamison saw his sister’s missing child poster on their computer screen, he mistook it for a FaceTime call and reached up to blow her a kiss. 

Harmony is described as being about four feet tall and weighing 50 pounds. She has blonde hair and blue eyes and should be wearing glasses. She’s also blind in her right eye.

Manchester police set up a tip line this week that will be manned around-the-clock by detectives at 603-203-6060. There was a $12,500 reward for information leading to her location announced Monday. By Tuesday evening, that total climbed to $33,000.