You keep writing words to the effect that "your first name is your legal name" with full cultural blinders on. I was born in Quebec (Canada) and, for many gene

You keep writing words to the effect that "your first name is your legal name" with full cultural blinders on. I was born in Quebec (Canada) and, for many generations, almost all boys from French speaking families were named Joseph second_name third_name Surname, and all girls were named Marie second_name third_name Surname. Most people use their third_name where you would use your first_name. Every legal document that I have (including my passport) is based on my "legal" third_name Surname.