When Guðný Erlendsdóttir was born on 3 December 1788, in Rangárvallasýsla, Suðurland, Iceland, her father, Erlendur Einarsson, was 40 and her mother, Guðný Pétursdóttir, was 33. She married Brynjólfur Brynjólfsson on 13 July 1817, in Vestmannaeyjabær, Suðurland, Iceland. They were the parents of at least 6 sons and 3 daughters. She died on 18 June 1844, in her hometown, at the age of 55, and was buried in Rangárvallasýsla, Suðurland, Iceland.