A 16 and 18 YO relative. What kind of life have they led to have the frame of mind to fatally stab 5 family members.That wouldn’t be an easy thing to do even for a trained adult. Unless they did it while they were sleeping, then maybe, but still.
My bet, relatives from central America where knives and machetes are every day tools.
Unfortunately, based on other recently reported murder cases involving otherwise affluent teenage males, the cause of the murders may turn out to be something so trivial as an argument over suspending their Game Boy/Xbox playing privileges.