Prince Jacques and Princess Gabriella cheered South Africa to victory on Sunday with their father Prince Albert II also lending support for his wife’s native team.
Princess Charlene shared an image on her official Instagram account of her and their twins at the game, during which South Africa beat Wales 19-16 to reach the final against England.
The Princess wrote: “BIG GAME TODAY!!! Wishing both teams the best of luck,” with a clover and kissing face emojis.
Both of the four-year-old twins were holding South African flags in the instagram pic.
South Africa will play England on 2nd November at the International Stadium Yokohama. Japan is the host nation for the 2019 Rugby World Cup.