Seventeen-year-olds Hassan Munshi and Talha Asmal flew from Manchester to Dalaman in Turkey last week with the suspected aim of joining Islamic State fighters.
Former Dewsbury MP Shahid Malik, a friend of both families, said the parents were “broken” by their sons’ disappearance.
He added: “This should serve as a wake-up call for parents to be more vigilant, because there are people preying on their children, grooming them in the same way that kids are groomed for sexual exploitation.
“This is not a natural thing for teenagers to be doing.”
Hassan is the younger brother of Hammaad Munshi, who was arrested by counter-terrorism police in 2006 at the age of 15 and later convicted over his role in a plot to murder non-Muslims.
Mr Malik said there was no evidence of a link between the brothers’ cases but added: “Whether it’s influenced Hassan’s own way of thinking, that’s only a question that he can answer.”
Imam Farooq Yunus, of the Zakaria Mosque in Savile Town, where the boys attended religious school, said they had been let down by the system.
He said: “I think we have failed. Not just the people in here – the whole system - the council, the police, the community. The society have failed these two children and somehow we should put things in place where if they do feel strongly, they know what to do.
“The fault lies in the wider community where we are not engaging with them.”
The boys are the latest in a succession of young Britons thought to have made their way to Syria and Iraq. The authorities estimate the total number of British citizens who have joined the IS cause to number about 600.
The North East Counter Terrorism Unit said extensive enquiries were ongoing both locally and with overseas authorities to trace the teenagers.
A spokeswoman added: “We are aware that large numbers of British nationals are travelling to the Middle East.
“These people are from across the UK and this problem is not specific to a particular area.
“We do know that some of those travelling are from Yorkshire.
“While these people may be travelling for a variety of reasons, travel to the Middle East for any purpose is extremely unsafe and strongly discouraged.”
The families of the two “ordinary Yorkshire lads” today issued pictures of the teenagers.
A statement released on behalf of the two families said: “Our number one priority is to get Hassan and Talha back home with their families and we implore anyone who may have any information whatsoever to get in contact with the police.
“Naturally, we are in a state of profound shock and are trying to come to terms with the predicament we find ourselves in and we hope and pray that no other family finds itself in our situation.
“These were just two ordinary Yorkshire lads who enjoyed the things that all young people enjoy at their age - both Hassan and Talha had a promising future, as an apprentice and an A-level student respectively, and we are praying they will be back with us soon and are able to realise that future.”
The families have urged parents to be extra vigilant, saying it is “near impossible” to know if children have been groomed and brainwashed.
Hassan is believed to be related to Hammaad Munshi, who was arrested by counter-terrorism police in 2006 at the age of 15 and later convicted over his role in a plot to murder non-Muslims.
The Metropolitan Police believe around 600 Britons have travelled to Syria and Iraq since the conflict began, while around half are believed to have returned to the UK.
Nine Britons - including the son of a Labour councillor - were arrested in Turkey last week on suspicion of trying to cross the border into the neighbouring country.
Waheed Ahmed was one of five adults and four children being held by Turkish authorities after they were stopped in Hatay province last Wednesday.
Meanwhile, teenage girls Shamima Begum, Amira Abase and Kadiza Sultana are believed to be inside Syria after flying to Turkey in February.
It is understood the Bethnal Green Academy pupils from east London were following another 15-year-old girl who travelled to Syria in December.