A 16-year-old boy who was captured on the battlefield in Syria this week with fighters for the Islamic State is not American, but is instead from Trinidad and Tobago, according to American officials and the boy’s sister.
The teenager was taken from the Caribbean nation to the war zone when he was 12 by his mother, who converted to Islam after becoming romantically involved with a radicalized man, Sarah Lee Su, the boy’s older sister, said in a phone interview.
After a four-year silence, she heard from them for the first time last month, when her mother contacted her on Facebook Messenger and sent a series of audio recordings that said the two were alive and pleading for help. She said they were hiding somewhere in Syria.
“I need money to help us get out of here,” Gailon Su, the mother, said in one of the recordings she sent to her daughter, which was shared with The New York Times. “If not me, your brother. He is innocent.”
The American-backed militia that announced the boy’s capture on Wednesday said he was among three American citizens apprehended in recent days in the battle zone fighting for the Islamic State, which is also called ISIS. But Pentagon and State Department officials said only one of the three — Warren Christopher Clark, 34, a former substitute teacher from Texas — was an American.
On Friday, two American officials said that Mr. Clark would soon be transferred to F.B.I. custody. He will be flown to the United States, where he will face federal charges in Houston, the officials said.
The 16-year-old, who was erroneously identified in a news release from the American-backed militia as Soulay Noah Su, an American citizen, is actually Su-lay Su from Trinidad, the boy’s sister said. She recognized him in a photo released by the militia, the Syrian Democratic Forces, she said.
A team led by Hany Farid, a Dartmouth College computer science professor, used facial identification software to compare the photo with images of Su-lay posted on social media and concluded with “high confidence” that the two were the same person.
Ms. Su, 23, said her mother and brother had fallen under the sway of a Trinidadian man who eventually persuaded them in 2014 to travel to the budding ISIS caliphate. “Once they got to Syria,” Ms. Su said, “they told me that this guy took their documents and destroyed them, and said, ‘You are now going to stay here and die.’”
In the audio recordings Gailon Su sent to her daughter, she said, “Everyone wants to be blaming me, that I did bad things to my children. I just married a man.”
According to a database maintained by Simon Cottee, a University of Kent criminologist, the mother and son were part of a group of 10 people taken to Syria by Anthony Hamlet; also included were Mr. Hamlet’s second wife, two of his daughters and three other boys, Mr. Cottee said.
After departing in September 2014, Mr. Hamlet appeared in ISIS propaganda, including in a photo spread in the terror group’s online magazine and in a video in which he is shown on his stomach, peering through the scope of a rifle.
“In my research on ISIS in Trinidad, one of my most striking findings is the block nature of the migrations to Syria and Iraq,” said Mr. Cottee, who is working on a book on jihadists from Trinidad, which has one of the world’s highest per capita rates of recruitment to ISIS. Mr. Cottee first noticed the captured teenager had a similar name to one in his database on Wednesday.
“It wasn’t just individuals going,” he said. “It was entire families looking to remake their lives in the so-called caliphate.”
Little is known about the mother and son’s time in Syria and the mother’s current whereabouts is unknown.
The boy’s Facebook timeline, which is sparse, reveals only a handful of photos that speak to possible military activity. Of greater interest to him appears to be posts about flashy hightop sneakers. Because Su-lay was 12 when his mother took him to Syria, “He didn’t have any say or agency in the matter,” Mr. Cottee said. “So he is a victim as much as a perpetrator in the Syrian jihad.”
The posts by his mother on her Facebook page, identified as authentic by her daughter, indicated more agency in her own radicalization as well as a willingness to support her son’s exploration of military activities.
In a post in 2013, a year before they left for Syria, Su-lay’s mother congratulated him on his excellent grades. A year later, she liked a photo that her son had posted, presumably from Syria, of a mounted rifle. The following year, she liked a photo showing him in what appeared to be military fatigues.
But in one of the final messages she sent to her daughter last month, Ms. Su said she did not want her son to fight.
“Yesterday some people stopped him and they want him to go and fight,” she said in the audio message. “I don’t want my child to be crippled.”