My great grandmother was Olga Marie Fjerdingstad, born in Copenhagen about 1869, daughter of Julius Fjerdingstad and Marie Bolette Jacobsen. My grandfather was Holger Christopher Petersen and he came to the US as a teenager.
He didn't know much about the Fjerdingstad family other than they were small in stature and called the "Small Grandparents" (and the Petersens were called "Big Grandparents") and that his grandfather Fjerdingstad had volunteered for and distiguished himself in both wars, in 1800's. He was given a medal by King Christian IX.
Holger wrote a family memoir that said his grandfather had been sent from Norway to Copenhagen to study art. I think he might have meant his great grandfather since the records I have seen online show that Julius was born in Denmark, not Norway.
Also, my mother had a polaroid picture that was of my grandfather's cousin who was a famous silversmith. That's all she ever said about it though, no name given.