According to German media there were four adults and four children in the aircraft, three children survived badly injured with two of those having been thrown clear of the wreck.
Absolutely horrible, particularly when children are involved.
Depending on their age, German law permits children to share or even sit on an adult's lap in such an aircraft.
Nonetheless doesn't seem safe to me to carry any passenger who cannot be provided with a proper restraint system, regardless of what may be lawful.
What do Saratoga operators say? Is this common practice?