The pair welcomed daughter Tallulah seven months ago after struggling to conceive at first.
"It is exciting news but early days," a friend told The Daily Telegraph.
The pair has yet to confirm the news officially, but the friend added, "Buddy and Jesinta are very happy."
When Jesinta announced she and Buddy were expecting their first child together, she revealed the journey to parenthood hadn't been easy.
"My husband and I are so incredibly excited and overjoyed to announce that we have a baby on the way," she wrote on her lifestyle app, JESINTA.
"The journey to get here hasn’t been easy and this little life is the greatest gift and we feel truly blessed and grateful that we will have a little angel of our own.
"We have both dreamt of this for a long time and while the 2.5 years have been physically and emotionally challenging, there’s nothing we would change as its brought us to this beautiful moment."
She continued, "The immense love we already have for our baby is indescribable and we can’t wait to meet our little miracle."
The couple, who married in 2016, has chosen to keep Tallulah out of the public eye and have not shared any photos of her on social media.
Jesinta has previously told the Daily Telegraph about how she's adjusted to motherhood, "In those first few months there really is no time for yourself, you really become very dedicated naturally to your child and all of their needs because they are so dependent on you."
She also spoke of her hopes for more children and added, "It took so long, I think by the end, it ended up being four years from the time we started trying to welcoming her."
"It was a four-year journey so I would totally be okay if it was just Tullulah because we love her so much and we dreamt and wished for her for so long."