Yesterday, a counter-terrorism source told The Straits Times that a key reason why male militants are willing to sacrifice their wives and children in their "martyrdom" was because they did not want their surviving spouse and children being placed in deradilcalisation programmes after their death.
Four officers and six civilians were wounded in the attack, East Java police spokesman Frans Barung Mangera said.
Indonesian President Joko "Jokowi" Widodo condemned the attacks as "barbaric" and vowed that authorities would root out and destroy Islamic militant networks. The person identified as D.O., who carried out the third church attack, was the leader of JAD's Surabaya cell.
The family had been in Syria, where Islamic State until recently controlled large areas of the country, said the national head of police, Tito Karnavian. The mother and her 17-year-old daughter were killed when a bomb handled by the father exploded prematurely.
This is because the JI, and now the JAD, whose members have pledged their allegiance to ISIS, are indoctrinated to remain in a state of war, said Universitas Indonesia terrorism expert Ridlwan Habib.
"Because their leaders are detained, their groups could be retaliating", said Karnavian.
During Sunday morning's attacks, one suicide bomber appeared to have been disguised as a churchgoer.
The family's father exploded a vehicle bomb, while the mother was with their two daughters aged nine and 12 and two sons aged 18 and 16 used a motorbike in an attack on another church, police said.
Police reported that a separate explosion on May 13 in a family dwelling in Wonocolo, a suburb of Surabaya, was a "premature" blast by another family plotting an attack on a "undisclosed target" in the city.
The Aston Martin DB11 AMR is your grand touring supercar
Aston Martin has revealed the new DB11 AMR at the Nurburgring as part of the opening of Aston Martin's new AMR Performance Centre. In addition to the regular version, the manufacturer will offer a special edition called Aston Martin DB11 AMR Signature Edition.
Police in Sidoarjo, near Surabaya, recovered pipe bombs at an apartment where a blast on Sunday killed three members of a family alleged to have been making bombs.
While the families involved in the attacks over the last 48 hours were not known to have traveled to ISIS' so-called caliphate, the "returnee situation throws up potential other charismatic recruiters", Barton said.
The use of children in attacks in Indonesia is a "big development, unlike anything that's happened before in domestic terror", said Greg Barton, Chair in Global Islamic Politics at Deakin University in Australia.
In all, 31 people have died since Sunday in attacks, including 13 suspected perpetrators and 14 civilians, police said.
The East Java Police have found a connection between the church bombings and Sidoarjo bombing. A video released by an Indonesian news outlet appeared to show the explosion centered on one of the motorcycles, flattening police officers and damaging another auto.
Over the past few years, ISIS has enacted a wave of attacks in Indonesia, many of which have taken place in the capital city of Jakarta.
Al-Qaeda has carried out the deadliest attacks in Indonesia, killing more than 200 people on the island of Bali in 2002.
"We've also seen children involved in executing political prisoners, and there's always been an appetite in Islamic State to use women and children".