The militants rammed an explosive-laden truck into the five-star hotel and exploded it, killing more than 50 people.
Mohammad Ashfaq, the accused behind the Marriott attack, had absconded to Afghanistan after the assault.
Ashfaq's sons - 17-year-old Suhaib and 10-year-old Suhail - were expelled from madarssa Abdullah Bin Abbas in Kamalia town, where they were to memorise the Quran, the Dawn said.
Qari Ghulam Rasool of madarssa said he was not aware that they were Ashfaq's sons.
More From This Section
Arshad, brother-in-law of Ashfaq, was picked up for his alleged involvement and having links with the perpetrators of Peshawar school massacre, the Express Tribune reported.
In 2008, he had been arrested by intelligence operatives seeking information about fugitive Ashfaq.
Two years ago, his son Suhaib was arrested when he was going to Afghanistan to see him. He was released after six months of interrogation.
Meanwhile, Arshad's mother Sughra Bibi told reporters that she could not even think that her son could be involved in the Peshawar school attack that left 148 people dead, mostly students.