Cayamora Maute, the father of Abdullah and Omarkhayyam Maute, was arrested at a checkpoint in Davao City. The 67-year-old was reportedly travelling with his second wife, his daughter and her husband when he was apprehended.
The Maute group has been fighting alongside militants from Abu Sayyaf since May 23 in an attempt to wrest control of Marawi City on the southern island of Mindanao and gain a foothold for Daesh in the Philippines.
More than 200 have been killed in the fighting -- 134 militants, 38 government troops and 30 civilians -- and much of the city has been destroyed.
Security forces hope the capture of Cayamora Maute will help bring an end to the siege.
"They now see their patriarch and they are holding hostages," Manuel Gaerlan, the Davao police chief, said. "I want to tell them, take care of your hostages and we will also take care of your patriarch."
The Maute group and Abu Sayyaf, who both swore allegiance to Daesh two years ago, have seized several hostages, including a Roman Catholic priest.
"The arrest of the patriarch of the Maute clan is a big blow to the Maute terrorist group," Brig. Gen. Gilbert Gapay, spokesman for the Eastern Mindanao Command, said.
- Daesh territory
Cayamora Maute was being taken for medical treatment in Tagum City when he was seized at the checkpoint in Sirawan, Davao City, the Inquirer news portal reported. Davao City lies around 160 kilometers (100 miles) southeast of Marawi.
The arrest came after a video was revealed showing the Maute brothers and Abu Sayyaf leader Isnilon Hapilon planning the Marawi attack.
The military said the footage, which was found on a mobile phone in the city, demonstrated the militants' intention to establishing territory for Daesh in the Philippines.
Meanwhile, the government called on people to stop sharing images of the pro-Daesh fighters destroying St. Mary's Cathedral in Marawi City.
Brig. Gen. Restituto Padilla Jr., spokesman for the Philippine armed forces, said the film was intended to "sow hatred" between Muslims and Christians. Most Filipinos are Catholic but there is a significant Muslim population on Mindanao.
"Let us not buy-in to the plan of these terror groups to inflame the feelings of our other religions," he said. "This is not a religious war. This is a terror attack on the city of Marawi and we must be clear about it."
Also Wednesday, Justice Secretary Vitaliano Aguirre II accused political opponents of President Rodrigo Duterte of possible complicity in the Marawi siege.
He called for an investigation into lawmakers Antonio Trillanes IV, Bam Aquino, Gary Alejano and Ronald Llamas over a meeting they held with Marawi City leaders three weeks before the attack on the city, saying it could have "sparked the terroristic acts in Marawi".
