Sylvia and Pete first announced they were expecting back in October last year, when they shared the news on Instagram.
“When you found out you’re getting a best bud for life. Oscar’s little brother due in April next year. We are so lucky,” Sylvia captioned a sweet snap of Pete, 38, holding baby Oscar.
"Beautiful news. Congratulations," captioned Jesinta Franklin, while Sylvia's Today Extra co-host David Campbell added: "Best news ever!"
The happy news came after Sylvia admitted on air that Oscar had been conceived via IVF, however it’s not known whether the couple used fertility treatment to conceive their second son.
"I know from my own personal experience of IVF that so much goes into having a successful embryo and having something sitting there that gives you the opportunity to make life for your family," Sylvia tearfully said during a segment about embryos.
"There's such an emotional attachment to those embryos, long before they become the baby or the child that you grow to love."
Sylvia later referred to her pregnancy struggles, while discussing baby number two on Today Extra, saying: “We're so thrilled after not the easiest path first time around; we're grateful for this gift, another boy.
"Two boys under two is going to be wild. If you have any advice how to handle the chaos, let me know!" she said.
Peter, who’s the younger brother of Today star Karl Stefanovic, met Sylvia at work when they were put together for co-hosting duties on Weekend Today.
He eventually popped the question on holiday in France in 2016, before the couple tied the knot in 2017 in an intimate ceremony at Kangaroo Valley in NSW.