They were the only two to escape unharmed from a brutal attack on April 16 at their Farmington Hills home.
The younger siblings of 19-year-old Tucker Cipriano are expected to testify Wednesday during the preliminary hearing for their brother and his 20-year-old friend, Mitchell Young.
Tucker Cipriano and Young are accused of beating Tucker's father, Bob Cipriano, to death and critically injuring his mother, Rose Cipriano, and 17-year-old brother, Sal Cipriano.
Complete coverage: Attack on Farmington Hills family
Police say the men broke into the home and used baseball bats in a gruesome attack on the family.
Tucker's young sister and Sal's twin are now expected to give prosecutors details about what happened that morning.
"The experience must have been horrific," said Dr. Gerald Shiener, a psychiatrist at the Detroit Medical Center. "A brother killing a father, a brother, killing a mother. Those things are terrible, and we have to talk about it in court ... brings up all those feelings again. It's not just talking about it, it's re-experiencing, reliving it and all the things come out in Technicolor, so it's got to be very difficult for these children to do so."
During the attack, police say Tucker's brother, Sal's twin, hid in a closet and called 911 while his 8-year-old sister fled to the basement.
This will be the first time the two will see their brother in court, face-to-face, since the tragedy unfolded this past month.
"It must be hard to give evidence against your brother, and it's also hard to know that your brother hurt the rest of your family and tore your family apart like this," Shiener said.
-- Tucker Cipriano and Mitchell Young both face murder charges.