Van Assouw survived miraculously but all others on board the Airbus A330-200 died when the plane flying from Johannesburg to the Libyan capital crashed just short of the runway early on Wednesday.
Van Assouw's family misfortune has attracted an outpouring of condolences in the Netherlands, which lost 70 nationals in the crash, including the boy's parents and 11-year old brother.
His family thanked officials and doctors but also asked for the media to respect their privacy.
"We have two kinds of sorrow to deal with, because Ruben is in a terrible situation, but we have also lost family members, our brother and sister and our nephew Enzo. The future will be difficult for us," the family said in the statement.
None of the bodies have been repatriated so far outside Libya as authorities said they were waiting for the relatives of the dead to provide details of distinguishing marks such as tattoos and scars, or DNA and medical records to help identify them.