Former footballer David Beckham will be the grandfather.
Nicole Pelts, the fiancée of the athlete's eldest son Brooklyn, said on his Instagram account.
Pelts, who posted a photo of herself in a wide dress with a 21-year-old boy, wrote a note "Baby B".
The couple, who are currently vacationing in Greece, are also preparing for their wedding.
Nicole is the daughter of American billionaire Nelson Peltser.
