Anna, who married Tim Robards after falling in love on the first season of The Bachelor Australia, shared the exciting news on Instagram.
"MY SISTER is having a BOY 💙 and we couldn’t be happier," she posted.
And the new bub might have a cousin joining him very soon.
Anna Heinrich and Tim Robards are hoping to start their family soon.
The pair - who said 'I do' last year in a lavish ceremony in Italy - told Confidential that children has always been part of their life plan.
"A family has always been part of our life plan," Anna told the publication.
Anna added: "It will probably be towards the end of this year that we start trying."