Three hundred letters were sent between Guðrún Lárusdóttir and Sigurbjörn Ástvaldur Gíslason in the early 20th century. Their correspondence, as preserved in the Women's History Archives, begins with a letter from Guðrún on February 28, 1900, and they begin by addressing each other as "dear sister" and "dear brother." They talk a lot about religion as Sigurbjörn was a priest and Guðrún a priest's daughter. Guðrún once wrote to Sigurbjörn that she wished she was a boy so that she herself could become a priest. 

Guðrún and Sigurbjörn got married on June 27, 1902 and had 10 children. Guðrún (1880-1938) was a writer and in Reykjavík's municipal council 1912-1918 and she was the second woman in the Icelandic parliament. She was a member of parliament for the Independence Party 1930-1938.  She was also the chairperson of the Women's Evangelical Association in Reykjavík from 1926, likewise until the end of her life. She founded the Reykjavík Housewives' Association and was its first chairman 1935–1938. Sigurbjörn (1876–1969) was a priest and founder of the retirement home Grund. He was chairman of the parish committee of Reykjavík Cathedral for 30 years, was in the executive committee of the Grand Lodge of Iceland, was a board member of the Union of Icelandic Christian Missionaries and chairman of the Children's Protection Council.

A selection of Guðrún and Sigurbjörn's letters is now on display in the library.