We had a gap in our history story between Caracalla and Macrinus so we filled it with a great new article, with lots of titbits some would not associate Caracalla with, like he is one of the reasons that 1000 years later Byzantines would still call themselves "Romans"....
Caracalla after the murder of Geta
In the short term the death of Geta weakened rather than strengthened the rule of Caracalla. The people were upset both by the crime of fratricide, and by the fear that the divine punishment for that crime might involve the rest of the empire as collateral damage. The army were upset, because the soldiers had sworn allegiance to both brothers. The senate, while not deeply disturbed by the death of Geta, was dismayed by the loss of so many of its members in the subsequent purge.
...to the full article of Caracalla after the murder of Geta