We called my paternal grandmother "Grandma Julia." When my mother started doing genealogy, she listed her maiden name as "Mary Julia KAIN." She is listed in every US Census record as "Julia." In the Social Security Death Index, she appears as "Julia Huigens." On her SS-5 application for Social Security, she listed her name as "Mary Julia." Our assumption has always been that, in typical Irish fashion, she used her middle name insted of the ubiquitous "Mary."
But on my father's birth certificate her maiden name is listed as "Julia Marian KAIN." Where did that come from? How am I supposed to assess that evidence? Did someone other than my grandmother provide the information for my dad's birth certificate? Did my grandmother unofficially change her name for some reason? What counts as an "official" name in the days before registered births?
My research plans for resolving this mystery consist of looking for a delayed birth certificate and baptism records from St. Ludger's Catholic Church in Creighton. I'd consider a baptism certificate to be more primary than any of the other documents. If a person starts using a different name than the one they were given at birth, does that then become their "official" name? I'm sure they would think so.
In any case, she will always be "Grandma Julia" to me.