Brendan Moody wrote:
RTD revealed his "big old plan" about Caecilius and Frobisher on the featurette for the Children of Earth DVD. It was just that Frobisher was a descendent of Caecilius, and the murder/sucide was the timeline finally "correcting" the Doctor's rescue of the family from the fixed point of their destruction.
It takes a couple of thousand years for the Timeline to correct itself? Couldn't Time Itself arrange for Caecilius and his family to get in a horrible accident on their way to Rome and be done with it? After all, Time Itself wasted no, well, time, correcting Adelaide's survival in Waters of Mars.