Fans flocked to the post, calling for the two to get back together.
'Just get remarried already,' one royal fan advised.
'I love these two - why don’t they get remarried ❤️❤️,' another added.
Sarah and Andrew separated in 1992 after just six years of marriage and divorced four years later.
A body language expert also commented on the overly friendly demeanor of the former flames.
Robin Kermode, a body language expert and communication coach, told Daily Mail: 'It's a real shared moment of fun.
'Prince Andrew’s comment has brought pearls of laughter from both women. Both are clearly relaxed and happy.'
Earlier this year, Fergie took to Instagram to wish her ex-husband a happy birthday.
'Happy birthday to the best man, father, friend Prince Andrew,' she wrote, adding 'Ooh, the best looking' and sealed the message with a kiss.
Fergie continues to live at Andrew's home at Royal Lodge in Windsor, where she has her own rooms along a separate hall. In 2014, the pair bought a £13million chalet in the ski resort of Verbier together.
While both have been in relationships since splitting in 1992, neither Andrew or Fergie have come close to remarrying.