Even if the girls have not initially implicated the brothers doesn't mean that they never had any involvement. The police can't hold the brothers further without good cause or evidence, which falls now to the crime scene investigators. One would expect that there is going to be DNA of one or more brother at the house, but the defense would counter that it is not unusual for the DNA of one relative to be at the house of another relative. An obvious alibi of a brother would be that even though he was at the house, the victims were either not present or they were silenced in another room. Without a direct implication by any of the victims, or reliable witness reports, prosecuting the brothers is going to be difficult. This is going to take a while to get to trial, and maybe something solid will come up on the involvement of others.
from what the perp’s son said, the 2 uncles are useless drunkards.
On one of the news show this morning, a neighbor took a reporter on a tour of her house - which is a replica of the crime scene. Didn’t look too big to me - and the camera tends to enlarge space. Also, it’s what I would call a “railroad” design - no hallways, just one room leading into the next. They didn’t show the upstairs but the kitchen led directly to the cellar.