But the former Barcelona player’s sister will not be there, Dias said, because she does not agree with his lifestyle.
Ronaldinho, who is said to have given both women engagement rings in January, apparently already lives with them.
The ceremony, at their £5m home in Rio Janeiro, is said to be for close family only.
Bigamy is punishable by up to six years in prison in Brazil.
It is thought unlikely that the ‘weddings’ will be officially registered, however.
Ronaldinho is said to have started dating Ms Beatriz in 2016, several years after he met Ms Priscilla.