According to PEOPLE, his poor health and his strained relationship with Eugenie's mother,Sarah Ferguson, are rumoured to be the reasons why he won't be present at the ceremony.
'He does what he wants,' a source told PEOPLE Magazine.
'He made a supreme effort for Harry. I would be very surprised if he did go, because he is so estranged from Fergie. I think he will decide at the 99th hour.'
Princess Eugenie's mother, the Duchess of York, was married to Prince Philip's son, Prince Andrew for a decade. The pair had two children together, Princess Eugenie and Princess Beatrice.
Sarah Ferguson spoke of her strained relationship with her former father-in-law to talk show host Doctor Phil after he called her 'idiotic' when she attempted to sell access to the royal family to an undercover reporter.
'The first person who said it was my father-in-law,' she revealed.
'For such a smart woman, why does she behave in such an idiotic way?' he said of the incident.
Princess Eugenie is due to get married on October 12 at St. George's chapel in Windsor Castle.