Heiman Sander(s) Leefsma was born in Gorredijk, part of the town Opsterland. He was a merchant and the son of Sander Heiman Leefsma and Betje Davids Kalf. He married Magalina Mossel in Utrecht on 3 October 1877. She was the daughter of Isaak Mossel and Sara de Vries.
The couple had 14 children, of whom one was stillborn. Of the other 13, five got killed in the war: Izaak, Hernrietta, Gerrit and J…