Gloves are off between Simone Holtznagel and Jonathon Castano

The relationship breakdown between model Simone Holtznagel and fitness trainer Jonathon Castano has gone from amicable to tumultuous.

The gloves are off. The relationship breakdown between model Simone Holtznagel and fitness trainer Jonathon Castano has gone from amicable to tumultuous.

Well-liked Holtznagel excitedly welcomed the arrival of her first born in March, taking to Instagram to share the news, writing: “On Sunday, March 31st, we welcomed our healthy baby girl Gia Holtznagel Castano into the world.”

“We are totally and completely in love with her and enjoying these special moments as a family of three,” she continued, sharing a snap of herself and then-partner Castano with their newborn daughter.

However nine months on, it’s clear Holtznagel and Castano’s relationship is fractured.

Simone Holtznagel’s Instagram post announcing arrival of baby Gia.

She has since altered “we” to “I” and changed Gia’s surname from “Holtznagel Castano” to just “Holtznagel.”

Following queries from Saturday Confidential yesterday, the model mum changed it back.

Holtznagel has also removed every post of her ex and doesn’t follow him on Instagram and he has removed all photos of her.

While Holtznagel wouldn’t return Confidential’s phone calls yesterday, those close to her say there is bad blood between the pair.

“He broke her heart,” one close friend said.

Just this week, Castano promoted a Sports Illustrated article he took part in, where he spoke about changing his diet to keep up with his daughter.

Jono Castano in Thailand just eight weeks after his baby was born. Picture: Instagram

“As I navigate this new chapter in my life, I prioritise planning and preparation when it comes to meals,” he said.

“I aim to include a variety of nutrient-dense foods in my diet, ensuring that I have the energy and stamina to keep up with my busy schedule and care for my little one.”

Rumours of a rift between the pair swirled just days after the couple’s baby was born after Castano posted a series of pictures of himself on a seemingly solo luxury Thailand trip, just days after Gia was born.

As one follower asked bluntly in the comments section: “Don’t you have a newborn baby? Where’s your girlfriend?”

Holtznagel, who is now living with her parents in Wollongong, isn’t the only person Castano is understood to have had a falling out with in recent months.

While it’s been well documented he and Rebel Wilson no longer talk, after he continued to use her name to promote himself and after claiming he was behind her new body. It is also believed he no longer talks to former clients Candice Warner, Steve Smith’s wife, Dani Willis or Michael Clarke. None of them follow him on social media.