Marinus van der Lubbe was born in Leiden in the province of South Holland. His parents were divorced, and after his mother died when he was twelve years old, he went to live with his half-sister's family. In his youth, van der Lubbe worked as a bricklayer. He was nicknamed "Dempsey" after boxer Jack Dempsey because of his great strength. While working, Van der Lubbe came in contact with the labour movement; in 1925, at age 16, he joined the Communist Party of the Netherlands (CPN) and its youth wing, the Communist Youth Bund (CJB).