His brother-in-law, Mukhlas, awaits execution in an Indonesian island prison for his role in the deadly 2002 Bali bombings.

And although Abas insists his family bond with Mukhlas remains intact, he concedes there's little warmth.

'He calls me an infidel. He says I'm not Muslim any more,' Abas says of Mukhlas.

Jemaah Islamiyah (JI) has long been a family affair, with deep roots extending back to early 20th century radical Islamism.

A police crackdown - including key arrests and the inducement of militants such as Abas to defect - has crippled JI and severed its links to foreign funds.

But while the network is diminished, analysts say JI has been able to fall back on a tight network of schools and marriages.

JI is now focusing on rebuilding its strength through family links and especially its network of Islamic boarding schools, according to Ms Sidney Jones, a terror expert at independent think tank the International Crisis Group.

'It means that even if you lop off the entire leadership you still have an organisation that has tight bonds between people,' she says.

'JI's schools and families are the main source (of support), it can't be denied,' says Mr Taufik Andrie, a researcher into Islamic militancy in Indonesia.

Without this network to fall back on, JI 'would be extremely weak compared to their current strength,' Mr Andrie says.

The Al-Mukmin Islamic boarding school in Ngruki, Central Java, founded by JI spiritual head Abu Bakar Bashir - who served a little more than two years in prison in connection with the Bali bombings - is a key hub in this network.

The classrooms of the school, which has about 1,500 students, are adorned with cardboard cutouts of AK-47 rifles and posters exhorting students to martyrdom.

The school's principal, Wahyudin, denies the school is linked to JI or that the radical network even exists - but he freely admits his own radical beliefs.

He says that he would like to visit the condemned Bali bombers in prison, but that fear of damaging the school's public image holds him back.

'Often I convey: why did the Bali bombing happen? It was a reaction, not an action. (The bombers) felt they had to defend their brothers and sisters in Afghanistan, old people, women,' he says.

Schools are key to membership of radical group
In a country where most Muslims adhere to a liberal strain of the religion, the school and others like it are far outside the mainstream.

While the Ngruki school recruits students from the wider community, it also draws from a core of families that have been committed to hardline Islam for generations.

'It's been clear from the beginning that school links are extremely important and, unlike the case with jihadi groups in other countries, schools are a key determinant of membership of JI,' analyst Ms Jones said.

'You can go through every class of Ngruki since the day it was founded and find people who joined JI.' Ngruki's most infamous cohort, the class of 1995, shows how JI's schools and marriage networks tangle.

Alumni include Muhammad Rais, who was involved in the deadly 2003 bombing of a Marriott hotel in Jakarta. His sister, Rahmah Rusdi, is the first wife of fugitive Malaysian-born JI mastermind Noordin Muhammad Top.

Another classmate, Asmar Latin Sani, blew himself up in the attack.

Another 1995 alumnus is Salahuddin al-Ayubi, who is currently imprisoned in Jakarta's Cipinang prison for assisting Noordin. His wife, Sarah, comes from another key part of JI's archipelago of schools: Al-Mutaqin in the Central Java town of Jepara.

The Jepara school is often looked to by JI members and leaders as a source of young women who can be married into the movement, terror expert Jones says.

'That's the classic school you go to if you want to get wives,' she says.

'Marriage has been from the beginning a very important bond that not only helps solidify the organisation but also, at least in JI's history, played an important security role,' Jones says.

'You looked for a partner that would protect the clandestine nature of the organisation.' That's a view shared by militants at the receiving end of the police crackdown. Imprisoned JI and JI-allied militants who replied to written questions said marriage plays a major role in forming bonds key to violent jihad.

'Besides ideological observations, I have felt and reached the truth that marriage has a value and benefit that is extremely strategic for furthering jihad activities,' wrote Enceng Kurnia, convicted over the 2004 bombing of the Australian embassy in Jakarta. -- AFP