Two girls, aged 13 and 14, appeared in a Newcastle court on Friday.
The toddler was reported missing from the shop in Newcastle.
A family acquaintance has been charged with kidnapping the teenage sisters.
Possible motives could include ransom or a prisoner swap, according to U.S. officials familiar with the investigation.
Asaib Ahl al-Haq, Kata'ib Hezbollah and the Badr Organization are the principle focus of the investigation.
Militants kidnap citizens after attacking government-held areas in the eastern Syrian city of Deir al-Zor.
Two seniors at the University of Rochester disappeared early Saturday morning.
Gunmen in Kenya abducted a former employee of the Norwegian Refugee Council in 2012.
His bodyguard, Nadrian James, was also arrested on similar charges.
The kidnappings are among the largest abductions on Cameroonian soil since last year.
Although no one has claimed responsibility, the attack bore the hallmarks of Boko Haram.
No one has claimed responsibility for the attack, but the blame will likely fall with Boko Haram.
The boy - who has ties to the country's political elite - reportedly managed to evade his kidnappers in the airport
As Algerian military and police search for kidnapped tourist, PM says France will not negotiate with militants
While Western prisoners get all the attention, thousands more have been snatched by ISIS
A high-ranking government official threatened to prosecute his mother and brother if they paid ISIS
Maxim Martsinkevich and his group 'Occupy Pedophilia' are notorious for kidnapping and humiliating young gay men and posting videos online
Guido Carlotto, one of millions kidnapped during Argentina's military regime, was reunited with his grandmother this week after 36 years apart.
Militant group attacked northern town of Kolofata on Sunday
A bomb blast hit a busy market in northeast Nigeria, killing at least eight people, while a businessman was arrested in connection with the kidnapping of over 200 schoolgirls.