Princess Caroline's press office confirmed the news via a statement. "Her Serene Highness Princess Caroline has the pleasure of announcing the birth of her grandson, born on 21 March 2013," the missive said before adding: "Both mother and baby are doing well".
The newest member of the Grimaldi clan won't be a potential successor to the Monegasque throne given that Andrea and Tatiana have yet to marry. Any future heir will be the child born to Prince Albert and his wife Charlene.
The baby has arrived at a special time for Monaco. The Municipality is preparing to celebrate its annual Rose Ball, and all eyes will be on first-time grandmother Caroline, who is expected to attend with her other children Charlotte, 26, and Pierre, who is 25.
The arrival of a royal baby in Monaco normally merits some fanfare: For Princess Caroline's baptism in 1957, four bishops and 15 priests presided. The ceremony took place amid the splendour of the principality's cathedral, which had been filled with 10,000 lilies and tulips for the occasion.
But new mum Tatiana's style is more low-key, and such a lavish display of pomp and circumstance is unlikely to surround her first child.
Instead, the family base will be in Paris, far away from the media spotlight. It was there that Andrea and his fiancée first fell in love while studying.
Much like Kate Middleton, Tatiana exudes humility and has perfected the art of being a discreet yet supportive consort. Her low-key approach is something the Monegasque royals – Caroline in particular – appreciate.
Tatiana is the granddaughter of the late Colombian mega-mogul Julio Santo Domingo, and is set to inherit an estimated $6bn fortune which she will share with her younger brother Julio Mario Santo Domingo III.
Despite her vast wealth she has worked hard to establish ethical fashion brand Muzungu Sisters, which she co-founded with business partner Dana Alikhani, daughter of the late Iranian businessman Hossein Alikhani.