When Lars Mogensen was born in 1791, in Nylarsker, Bornholm, Denmark, his father, Jens Joensen, was 35 and his mother, Engelica Joensen, was 38. He married Ana Magretha Olsdatter on 25 May 1821, in Copenhagen, Copenhagen, Denmark. They were the parents of at least 2 sons and 5 daughters. He lived in Vestermarie, Vester, Bornholm, Denmark in 1845 and Rønne, Bornholm, Denmark for about 10 years. He died on 17 January 1861, in Nylarsker, Bornholm, Denmark, at the age of 70.