Erling Tjaaland

I am looking for my husband's family, but don't know where to go from the information that I have. I know his great grandfather was Erling Johaan Tjaaland (b 13 Dec 1896) and he married Elise Kristine Karlsen (b 1892). I know they were both born in Stavanger and married April 25, 1918. I was able to find the immigration records where they came to America with their children (my husband's grandmother and her brother). From their marriage records, Erling's father was Johan Tjaaland and Elise's father was Zakarias Karlsen. I also know that he had something to do with fish packaging and opened several factories there to do that. Can anyone help me go any farther back from this? Thank you!