I can not figure out where did you get your information.
Spyro Capo D'Istria, the son of Viario (NOT BIARIOS) was born 1651, 100 years before Ioannis GG.
Ioannis had no children. He had a brother Viario (a Lawyer) who was born 1774 (Children Unknown).
There is NO spyros/Angelos "Combo" As you say. Angelos is not a common name in the family. There is only one Angelo that I know, the last 400 years
There is an Army officer called Spyro (Spyridon) who was born 1709, son of Dr. Antonio and Belanda Petretin.
Listening to theories is not the right way to search your history.