Peter Martin Herstad

Hi! :-) I am new and am trying to find info on my gggrandfather Peter Martin Herstad b. abt 1838 in Trondheim or Stjordalen, Norway and buried near Stjordalen in the Vaerdal Churchyard. He married Sofie Christiane Einersen on 7/2/1867 and had 4 children-Aksel, Fredrikka, Petra and Anna. I have found some info on the 1865 and 1900 censuses, but still can't track down his parents. Our family writings say that his father was a "standard bearer for the King" and his mother was a "Danish Baroness." I would like to find out if this is true. Can anyone help? It would be much appreciated!