'I watched my twin sister take her final breath. I wasn't prepared for what happened after.'

In Karen's final moments, Kylie knew exactly what she needed. Her sister was lying silently in her bed, which had been manoeuvred into the living room.

Kylie had lit candles, diffused oils, and administered Karen's medication with the precision of a former nurse. But, by the look on her sister's face, she knew the pain lingered.

Instinctively, Kylie unlocked her phone and pressed play on an old playlist. As the first note sounded, a smile materialised on Karen's face.

Her two sons, four and seven, sat on the edge of her bed. Her two nieces, Kylie's daughters, weren't far away. The living room was a cacophony of music and conversation.

These were the last sounds Karen heard before she took her last breath, surrounded by family and love. Her debilitating health battle had finally ended — two years longer than she had been told it would.

But no amount of time could prepare Kylie for the way her world was about to change.

Watch: The Grief That Comes With Life Transitions. Post continues after video.

Karen was 37 when she was diagnosed with a rare form of cancer. At the time, she was given just a five-month prognosis.

Her twin sister, Kylie, still remembers the moment she found out.

The mother-of-two, who was visiting a friend in Hawaii, had just sat down for a cocktail.

As she went to take a sip, her phone lit up with a FaceTime from her husband, who was in Australia with their daughters.

"Immediately, from the look on his face, I knew something really bad had happened," Kylie told Mamamia.

Karen, had gone into surgery earlier that day to remove fibroids from her ovaries. Except, they weren't fibroids.

"They were a Krukenberg tumour," Kylie said (a rare type of metastatic ovarian cancer).

"I was on the next morning flight home."

From the moment she touched down, Kylie never left her twin sister's side.

"People marvelled at how I was at every appointment, hospital visit and step along the way. The truth is, I had to be," she said.

"It wasn't a decision, it was an unsaid code."

"We were always in it together, even when we were apart."

Growing up as twins, Kylie and Karen had a "dual identity."

They were "The Twinnies" or "The O Twins."

They shared a secret language. They had the same friends. They even went through breakups at the same time.

"One of us rang the other… I can't even remember, that's how intertwined our memories are… and said, 'Oh my god, we've broken up.' And the other one said, 'Get out. Same here!'"

The twins promptly moved in together until they met their future husbands. Later, when they both welcomed children, they were each other's birthing partner.

"When one of us was going through something big, the other one was just always there," Kylie said.

"That's your DNA. It's just this interconnectedness that is never questioned. You're doing that for yourself as much as you are for her, because that's a part of you."

"That's your DNA. It's just this interconnectedness that is never questioned." Image: kyliebrennan.com.au

Karen's cancer treatment, which involved two major surgeries, chemotherapy, and radiation, was an "awful, gruelling two years on her body."

Throughout that time, she wrote a book for her sons, who were too young to fully grasp what their mother was going through, to explain her diagnosis in a language they could digest.

Kylie, meanwhile, understood all too vividly.

"It was very hard to watch her go through that, but I would not be anywhere else," she said.

When Karen received radiation in her shoulder, Kylie "experienced excruciating pain in the same spot."

"My family noticed when they touched the skin that it was hot," she said. "It was strangely comforting to know the treatment had not changed the deep rapport we had, and the 'twin thing' that had us feel each other's experiences."

Karen's death saw Kylie's "whole world" crumble.

"Half of my experiences, memories and DNA died with her."

"Existing in the world without her meant I felt alone, lost, and half of every part of my world."

On the day of the funeral, which coincidentally fell on the anniversary of Karen's surgery, Kylie asked to accompany her twin's casket in the hearse car.

"I didn't want to be away from her body," she said.

Sadly, her request was denied as the vehicle didn't have enough seats. It was the first of many moments Kylie had to learn to be apart from her twin.

As the world went on around her, Kylie's grief was compounded with a "confronting crisis of identity."

"This grief is classified as 'complicated' because twins have always been a 'we' as part of who we are," she said.

"We can't be who we are anymore without the other. This grief makes you lose your person, then it makes you lose who you are and how you fit into the world.

"It's cruel and lonely."

Amid the darkness, Kylie realised that Karen's "legacy is too important" for her to be consumed by the isolation.

"It made no sense for me to stop existing. If the roles were reversed, and I watched her stop living, that would be horrendous. I couldn't deal with that," she said.

Kylie decided that she "didn't need people to understand [her] grief." It was for her and Karen alone.

"I was able to build a very strong connection to her and to who I'm supposed to be now. I really feel like that allowed me not to be swallowed into this isolation."

"It made no sense for me to stop existing. " Image: Supplied

Making this decision wasn't about leaving Karen behind, but to "carry her" forward.

"This was beautifully captured by our friend who said, 'They were inseparable in life, who are we to say they're not now?'"

Today, Kylie feels Karen through signs; sunflowers that appeared right after her twin's death, and have persisted since.

"One day, my husband and I were driving, and he said, 'What if it's just you choosing to see sunflowers?' And I said, 'But, by me choosing, I'm actually bringing her into my thoughts. So, isn't that a good thing?'"

Amazingly, at that moment, the couple drove past a mural full of sunflowers.

"I said to him, 'Kazzy doesn't like that.'"

As a mindset coach, Kylie acknowledges there is confirmation bias involved, but still sees the sunflowers "a beautiful symbol of sharing both of our legacies."

Kylie has also joined a community for people who have lost their twins.

One organisation of this kind was created by Dana, who lost her 25-year-old twin in 2024.

"The day she died, I said to my partner, 'I think Monique's dead,'" Dana told Mamamia. "And he was like, 'No, you're just being silly.'"

But, at 10pm that night, Dana received a call from her grandfather; Monique had died in a motorcycle accident.

"It was like my whole world had fallen apart, like this big part of me is gone. I don't really know who I am any more," said Dana, who struggles with survivor's guilt to this day.

Looking for support, Dana stumbled upon the Twinless Twin Support Group.

Realising the organisation was internationally based, she created a Facebook group specifically for people in Australia, where Twinless Twins can "connect with others who truly understand… and celebrate the lives of [their] beloved twins, ensuring that their memories live on."

Feature Image: Instagram/kyliebrennancoaching