It’s a boy!
The 35-year-old married the Swiss businessman last month.
The former royal took to Instagram on Thursday and shared a beaming selfie with her spouse and their new baby.
"Our little Theodor," she captioned the snap.
De Nassau’s eldest son, Prince Gabriel, previously shared the news in a video message on his mother’s social media page.
"Frank, our children and I are happy to announce that our little bean has arrived," his mother captioned the post. "Theodor is healthy and a very active little man. We are over the moon with joy."
De Nassau’s ex-husband also had a recent life update. Back in April, the Grand Ducal Court of Luxembourg announced that the 35-year-old was engaged to French lawyer Scarlett-Lauren Sirgue, 29.
"We are very happy to announce the engagement of our son, Prince Louis, to Miss Scarlett-Lauren Sirgue," the prince’s parents – Grand Duke Henri and Grand Duchess Maria Teresa of Luxembourg – shared in a statement. "[Louis's sons] Princes Gabriel and Noah join us in surrounding the new couple with all our affection. We wish them immense happiness."
At the time, De Nassau also shared a message of congratulations on her Instagram story.
"Finally its out too," she wrote. "Gabe, Noah, Frank and I are so happy for you both and wish you only the best and much happiness.
Louis and De Nassau were previously married from 2006 until 2019. The former couple met while they were both serving in the army. They share two sons.
Since her divorce, Antony has taken on the roles of humanitarian and businesswoman. She launched a podcast titled "Tessy Antony de Nassau’s Zoom O’Clock" in 2020.