Complex sentence: Mary Björnström-Steffansson died in 1953 and at the time of Mauritz Håkan's death in May 1962, their house on East 57th street was one of the few remaining private houses on Manhattan island.
Split into simpler sentences: Mary Björnström-Steffansson died in 1953, Mauritz Håkan in May 1962. At the time his death, the couple's residence on East 57th Street was one of the few remaining private houses on Manhattan island.