Fears of reprisals by the Headhunters gang that Morris belonged to remain high. Fresh threats have been made on social media.
A family friend of the boys, who spoke on condition of anonymity, claimed they were "being looked after by police".
"All I know is that they're fine. They weren't involved in [Morris' death], but [are keeping their heads down] because of the involvement with those that are."
The brothers lived in a sleepout behind the home, .
It is understood they have been formally interviewed by police. One of the two had just become a father.
Police kept guard over the house for a week after the August 2 killing of Morris, a patched member of the Headhunters motorcycle gang.
But this week, the property was deserted. Glass covered the driveway and an overturned table had apparently been used as a barricade. The back door window was smashed.
The McDonald's wrappers and rubbish strewn across the backyard contrasted with the flowers laid on the grass verge in front of the house as a tribute to Morris.