Justin Hemmes' pregnant girlfriend Madeline Holtznagel gets in some practice as she dotes over her sister Simone's daughter Gia

She is set to welcome her first child with billionaire bar tsar Justin Hemmes next year.

And Madeline Holtznagel got in some practice over the weekend.

The model, 27, was seen doting over her niece Gia as she spent time with her sister Simone.

Simone posted sweet photos of the ‘Holtznagel family Christmas’, which included two of Madeline unwrapping presents with the tiny tot. 

The mum-to-be hid her baby bump in the photos as she donned a summer dress for the holiday occasion.

Meanwhile, baby Gia looked as cute as a button in a candy cane themed outfit and red and green bows in her hair. 

Simone captioned the image: 'We love aunty Madeline'. 

Madeline and Justin's baby joy was confirmed last month. 

A source confirmed the exciting news to Daily Mail Australia and revealed a friend of Justin's moved out of his Vaucluse mansion to make room for their growing family. 

The hotelier already shares two daughters -  Alexa, nine, and Saachi, eight - with his model ex Kate Fowler - the sister of Georgia Fowler.

It will be Madeline's first child.

Justin and Madeline's representatives told Daily Mail Australia the couple will not be making an official comment. 

Madeline is the younger sister of fellow Aussie model Simone, who welcomed Gia in March with her now-ex-boyfriend Jono Castano.

Justin and Madeline quietly began seeing each other in 2019, a year after his debut on the Financial Review Rich List with an estimated net worth of $951million - which has since risen to $1.39billion.

Though they generally keep their romance under wraps, the couple are often seen disembarking from his sea plane after enjoying luxurious family holidays with his two daughters.

In August, Madeline also made a rare public post about Justin as she took to Instagram to mark his 52nd birthday. 

She shared a series of romantic selfies of them both and gushed over her partner in the caption.

In one picture, Madeline flashed a huge smile as she sat on Justin's lap while he lovingly gazed at her.

Another showed the pair cuddling up to one another as they relaxed on a yacht.

'Happy birthday my love,' she wrote in a caption along with rose emoji. 

Earlier this year, Madeleine celebrated her 27th birthday party with a lavish bash at Justin's sprawling Vaucluse estate.

Following the festivities, she revealed that her doting partner had bought her two llamas as a sign of his love.

The couple have gone from strength-to-strength since going public in 2019 and even sparked engagement rumours last June. 

Eagle-eyed fans noticed Madeline was wearing a ring on her wedding finger as they questioned whether Justin had popped the question.

A picture showed her sporting the jewellery as she cuddled up to Justin while enjoying a bowl of Udon noodles together at a restaurant in Japan.

But the bling appeared to be an emerald and diamond promise ring, and another photograph showed her wearing a different ring on the same finger as she posed for a selfie.

Justin was previously in a relationship with Kate Fowler and the pair remain on good terms, often jetting off on holidays together with their daughters Alexa and Saachi.

Just last month, Justin and Madeline were joined by Kate and her new boyfriend David Oettlé as they took Alexa and Saachi to Queenstown, New Zealand. 

Justin and Kate dated for three years before going their separate ways in early 2018, with Justin issuing a statement about their split at the time.

'Kate and I have the utmost love and respect for each other,' he said in a statement given to the Sydney Morning Herald.

'At the beginning of 2018, Kate and I decided our friendship and respect for family life would become the focus of our relationship. 

'We love our children dearly and for now continue to live together happily in our family home.'

'Kate is a wonderful, wonderful, wonderful woman. As for what the future holds I am not sure,' he added. 

Justin is considered Australia's hospitality king, with more than 80 venues and billions in assets with names like the Ivy, Queen Chow and Establishment under his purview as CEO of Merivale.

He is the only son of Merivale Group founder and nightclub mogul John Hemmes and Justin took over the business after his father's death in 2015.