Research Notes:

The Historia Brittonum and the Annales Cambriae... state that Eowa was a king of the Mercians himself at the time of the Battle of Maserfield (or Cogwy), in which he was killed, on August 5 of what was probably the year 642. The later Mercian kings Ethelbald, Offa and Ecgfrith were descended from Eowa; the period of their rule began in 716 following the death of Penda's grandson Ceolred and ended with Ecgfrith's death in December 796.

It is possible that it was customary among the Mercians until this time for there to be more than one king, and Penda and Eowa may have ruled over the southern and northern Mercians respectively.