Kayla Itsines shares footage of her daughter Arna meeting her newborn brother Jax for the first time

There were tears, laughter and heaps of joy as fitness queen Kayla Itsines brought her newborn son home on Sunday.

Following the birth of Jax on Thursday, the 31-year-old and her fiancé Jae Woodroffe introduced their baby boy to his big sister Arna.

The fitness entrepreneur shares daughter Arna Leia Pearce, three, with ex Toby Pearce.

Kayla Itsines (pictured), 31, and her fiancé Jae Woodroffe introduced their baby boy to his big sister Arna on Sunday after the fitness queen gave birth last Thursday

Kayla captured the adorable moment the half-siblings met in a video uploaded to her Instagram page.

“Meet our precious little boy with the best big sister in the world,” she captioned the post.

Her famous friends couldn’t help but gush over the sweet footage.

Australian actress Teresa Palmer wrote: “Awesome congratulations, beautiful”.

“Congratulations, nice, that’s just really special,” said media personality Sally Obermeder.

All of it. You all… so much joy,” said one follower.

Kayla went to the hospital around 6.30am on January 5 before her son arrived at 8.45am weighing 3.5kg (7.72lbs).

She had undergone a planned cesarean birth after being scheduled early last year.

Kayla captured the adorable moment the half-siblings met in a video uploaded to her Instagram page

“Most amazingly, when it came out of nowhere on a completely random playlist that the hospital was playing, Jae’s father’s funeral song started playing over the speakers,” she said.

At the same time she heard Jae announce that it was a boy.

“I burst into tears, he burst into tears, and we got to meet our little boy,” she said.

“Meet our precious little boy with the best big sister in the world,” she captioned the post

Kayla said the surgery meant she would focus on lower-intensity workouts while she regained her strength.

In July, Kayla announced her pregnancy by holding up an ultrasound image with Jae as the two kissed.

Kayla became a multi-millionaire after the success of her workout app, Sweat.

Kayla went to the hospital around 6.30am on January 5 before her son arrived at 8.45am weighing 3.5kg (7.72lbs).