Looking Family of Hans Ferninand Throndsen

My grandfather was from the village of Kragero near Oslo. Looking for any family he may still have there. My grandfather changed his name to Thronson when he came to the USA in 1908. He had an older Brother that settled in the New York area, but we can't find any info on him. His first name was Petro or Pedro or something similar to that.. My grandfather and his immediate family were listed in the 1900 Norwegian census, but his brother had already came to the USA. My grandfather died in 1956 at the age of 69. He is buried in Hattiesburg, Mississippi. His father and my great grandfather was a brick mason by the way in Norway.