Sorry lookout it just doesn't happen that way. Paranoid schizophrenics don't plan to kill five people in advance,the twins murdered conveniently in their beds so that Jeremy doesn't have to face them running around the Farm. It's so obviously Jeremy's handiwork even putting Julie's statement to one side for the minute.
That's right,Steve,,they don't plan,,,they do it on impulse,spur of the moment and can annihilate a whole family. It would have spilled over out of control after their evening meal when Jeremy had gone.