SiliconEra has a nice writeup, on the main choices they made, in regard to 'Patroklos and Pyrrha' and 'Natsu and Taki':
In the case of Patroklos and Pyrrha, the two were chosen because they were Sophitia’s son and daughter. Sophitia, having a connection with the Soul Edge and Soul Calibur, plays an important role in the series, and her children gave the development team a reason to continue the Soulcalibur story.
The decision to include Natsu came from deciding that Taki would likely be too old to be a ninja anymore. In Odashima’s mind, you can only be a ninja up to a certain age, after which you retire from active duty and focus on training younger ninjas. While Taki has retired, she’s still watching over Natsu, he adds.
Share Link: 
