I mean if you want to get pedantic about his Roman name and title(tria nomina), then it should be written, Thadius Primus. Or Thaedius Primus for the correct spelling. The ‘ius’ change conveys a continuous family name; can be seen as a last name or representing “jr.” or “first of his name and family”(which makes Primus redundant. It’s like writing Sahara Desert).
I mean if you want to get pedantic about his Roman name and title(tria nomina), then it should be written, Thadius Primus. Or Thaedius Primus for the correct spelling. The ‘ius’ change conveys a continuous family name; can be seen as a last name or representing “jr.” or “first of his name and family”(which makes Primus redundant. It’s like writing Sahara Desert).