Sophie Cachia says there's one person who knows the sex of her next baby.

There are just 10 weeks to go until baby Cachia #2 makes his or her entry into the world.

And while The Young Mummy’s Sophie Cachia and her husband Jaryd are keeping the gender a mystery, there’s one member of the household who thinks they’ve got it all figured out.

Speaking to Mamamia on Friday, the 26-year-old blogger said the couple’s two-year-old son Bobby is adamant Mum is having a girl.

Sophie and Jaryd Cachia. Source: Instagram.

"I say to him, 'Is it your little brother or is it your little sister?' and he always says, 'That's my sister!'," Sophie revealed.

"He rubs my belly and says 'Hello little sister.' I haven't prompted him to do that ... he always says, 'Not my brother, that's my sister!'"

Sophie, Jaryd and Bobby Cachia. Source: Instagram.

Despite Bobby's guesses, many of the star's 250,000 followers think the now Melbourne-based family is destined for another boy.

"Everyone thinks we do [know the gender] because I always slip up and say 'he' because I think I'm just so used to having a boy in my life that I call this baby he all the time," she said.

"But we honestly have no idea."

Sophie and Bobby Cachia. Source: Instagram.

"It's funny — with Bobby we never wanted to find out, Jaryd and I never even had that discussion. But this time around I think I was a little bit more tempted, but Jaryd was still a definite no," Sophie continued.

"Then we had the 20-week scan and we both nearly caved, but I'm so glad we haven't because I just think that surprise you get on the day; I don't think there's a better feeling in the whole entire world."

So it looks like we'll all just have to just sit tight for another ten weeks to see if Bobby Cachia really is the baby whisperer.

To celebrate the birth of baby number two and raise some much-needed help for the less fortunate mums out there, Sophie is hosting a fundraiser baby shower on 17 November. All money raised from ticket sales will go directly to St Kilda Mums. Tickets and further information on the event can be found at Eventbrite.