Bjornlaug was born 13 June 1861. Her parents are Eyjolfur Gudmundsson, born 11 October 1829 in Illugastadir, Tjorn a Vatnsnesi, Vestur Hunavatn, died 19 October 1913; and Valgerdur Bjornsdottir, born 9 September 1828 Litla Borg, Breidabolstadir i Vesturhopi, Vestur Hunavatn, died 11 December 1916.
Bjornlaug immigrated to America with her parents Eyjolfur and Valgerdur; they had joined The Church of Jesus Christ of Latter-day Saints in 1883. Eyjolfur and Valgerdur and eight of their children emigrated to Spanish Fork, Utah via North Dakota and Helena, Montana. Somewhere in their travels to Utah, Bjornlaug must have met Boas Arnbjornsson, born 3 August 1855 in Ytri-Kleif, Eydalir i Breiddal, Sudur Mula; they showed up in Spanish Fork together in 1885. Boas’ parents are Arnbjorn Sigmundsson, born in 1810; and Gudny Erlendsdottir, born in 1819. They were married on 6 September of 1885. They changed their last name to Anderson.
They had seven children: Bjorn Nul (1884-1885), Thurren Gudrunbjorg Runolfsson (1886), Elenbjorg Ellen, Kari (1888-1966), Boas Eyjolfur Bruce (1891-1937), Valgerdur Audbjorg, Richter (1893-1959), Valdemar George Washington, (1895-1979), and Rose (1897-1969).
Bjornlaug was a fun-loving and always had a sense of humor. Like the rest of the family, she loved music and would often sing to the children. Like many Icelanders Bjornlaug was superstitious. She had a large leghorn rooster which she believed would come to the kitchen door and crow when someone was coming for coffee.Boas died 28 March 1908. Bjornlaug married Runolfur Runolfsson 16 September 1921. Runolfur was born 10 April 1851 at Draumbaer, Vestmannaeyjar. His parents are Runolfur Magnusson, born 22 February 1818 in Kross, Rangarvalla, died 20 March 1894; and Ingiridur Bjornsdottir, born in 1817 in Vestmannaeyjar, died 4 July 1870. Runolfur died 20 January 1929.
Bjornlaug died 23 November 1942 in Spanish Fork, Utah and is buried in the Spanish Fork City Cemetery. Bjornlaug went by Legga Anderson or Lauga Anderson in Utah. She is number 2 in Icelanders of Utah.