A little more info - I came across a paper that uncle/cousin Michael Deildal gave me years ago. He had found that Vigfus Sveinsson was adopted at age 4 by his mother's brother's family. His mother's name was Anna Petursdottur, so the brother would have been Petursson. It was common practice in Iceland at that time to give a child to a relative who did not have any children.
I also found out that they lived in a town called Enni in an area called Skagafjardar in the northernmost part of Iceland.
From: Linda Taylor