Blofeld had one daughter, Nena, who appears in John Gardner's continuation novels. She married a man named Bismaquer, but succeeded her father as head of SPECTRE.
Surprisingly, Wold Newton scholar Win Scott Eckert has actually identified Blofeld as a close relative of James Bond, both being descended from General Sir William Clayton, who may also have been grandfather of a man identifable as Lex Luthor. Eckert has found that Clayton's daughter Aspasia was Blofeld's great-grandmother. Blofeld's father was Baron Karl von Hessel (believed to be one and the same as Wolf Larsen, believed to be the son of Professor Moriarty).