Thomas Markle could form part of the defence and testify against his daughter in a legal battle launched by the duchess over privacy.
Thomas Markle said he had broken the news to Meghan in an emotional phone call just days before she was due to walk down the aisle in Windsor Castle's St George's Chapel.
Ms Markle asked The Prince of Wales to give her away after her father is no longer able to attend the wedding.
In a statement released by Kensington Palace, the bride-to-be spoke of her sadness that Thomas Markle would miss her big day.
Thomas Markle suffered an apparent heart attack last week and it is claimed he will undergo surgery in the US.
Meghan Markle's family has links in both America and the UK