The child will be the seventh grandchild for Princess Caroline and the second grandchild for Dimitri’s mother, glamorous French actress and former Bond girl Carole Bouquet.
Charlotte, who is ninth in line to Monaco's throne, and the film producer met in December 2016, and began dating shortly after.
Both Charlotte and Dimitri have children from previous relationships.
Charlotte has a 4-year old son, Raphael, with comedian Gad Elmaleh, and Dimitri has a daughter from his marriage to model Masha Novoselova.
Last year, Charlotte was embroiled in a baby scandal will Hollywood actor Brad Pitt.
In December 2017, sources claimed that the two were 'desperately trying for a baby'.
‘Charlotte already has a young son with her former partner and would love another baby, a sibling for little Raphael,’ a source explosively said at the time.
‘Brad loves being a dad and would love another baby. With everything that’s happened with Angelina and the messy custody battle over their six kids, it’s made him realise more than ever how much he enjoys having children around and how much he misses having little people running about.'
Brad and Charlotte – the granddaughter of the late Grace Kelly – reportedly met through mutual friends, with sources confirming that they were introduced by Brad’s Allied co-star Marion Cotillard. It’s believed the French actress and the Monaco royal are close friends, and Marion was keen to introduce them to one another after seeing the terrible pain that Brad’s marriage breakdown had caused him.
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