‘Are we sisters?’ The DNA test that exposed a family secret

Casey O’Connor and Alana Horton grew up as inseparable cousins and neighbours, often being told they looked remarkably alike
A DNA test revealed Casey’s dad was not her biological father, before a second test confirmed Alana was actually her half-sister
The discovery also revealed Casey’s uncle was her biological father

Here Casey O’Connor, 37, NSW tells her own story in her own words

Dancing around the living room with my cousin Alana, then six, singing along to the Spice Girls, we were having the time of our lives.

Living next door to one another, we were just 18 months apart and completely inseparable.

When we weren’t making up silly dance routines and performing them for our families, we were playing dress-up and having sleepovers.

‘You two could be twins!’ friends commented on our strikingly similar smiles and blonde locks.

While Alana had one older sister, I was blessed with three brothers.

But I was grateful to have a special sisterly bond with Alana.

two girls taking a selfie — Alana and Casey discovered a family secret! Credit – Supplied

READ MORE: A DNA test found my girl’s sperm donor, then he became my soulmate!

As teenagers, we loved experimenting with recipes in the kitchen – some edible, some destined for the bin.

After school I went on to study business, while Alana started her family.

In 2020, aged 31, I was working in corporate travel when my phone buzzed.

It was Alana.

‘Can you find somewhere quiet to sit? I have something to tell you,’ she said, urgency in her tone. But nothing could’ve prepared me for what came next.

‘I think your mum and my dad had an affair,’ Alana blurted, explaining her mum – my mother’s sister – had recently confessed her suspicions.

‘That’s crazy,’ I replied, putting it down to one of our family’s silly stories.

Getting back to work, I pushed the suggestion from my mind.

There’s no way, I thought.

It wasn’t until I was diagnosed with premenstrual dysphoric disorder (PMDD) a hormone-related mood disorder in 2024, that I wanted to dig deeper into my family’s medical history.

That’s when Alana’s story sprang back to mind. Finally, I felt ready to face it head on.

Heartbreakingly, I’d lost Mum in July 2017 to complications of a long-term autoimmune disease.

two girls sharing lunch — Alana and Casey were so close growing up. Credit – Supplied

Confronting my dad with the theory, we made a pact to find answers together and, in February 2025, Dad and I ordered DNA test kits from ancestry.com.

Spitting into a test tube each, we packaged up our samples separately and sent them off for testing.

‘Now we wait,’ Dad said supportively.

It wasn’t until two months later, that I received an email with my results.

Road tripping around Ireland at the time, my heart pounded in my chest as I scanned the page for answers.

That’s when I saw it… The man who raised me – my dad – wasn’t my biological father.

‘I had my suspicions about the timing of your conception,’ Dad admitted.

‘You’re my daughter. This doesn’t change anything,’ he soothed.

But that wasn’t all.

two women inside — Casey and Alana together. Credit – Supplied

Results confirmed I shared DNA with Alana’s dad – my uncle.

While Alana’s mum and my mum were sisters, Alana’s dad shouldn’t be related to me…

By now I’d started sharing videos about my DNA journey on my Tiktok @caseyooo.

Almost overnight, people from all over the world were resonating with my story, and sharing similar family secrets of their own.

‘Does this mean we’re sisters?’ I asked Alana on video call later that night.

‘There’s only one way to find out,’ she agreed.

So she took a DNA test, but it was another two months before results confirmed what our hearts already knew. Alana and her sister, were biologically my half-sisters.

‘I can’t believe it,’ we both said.

woman in black and white dress — Casey, recently. Credit – Activated Visuals

While I was full of excitement knowing I finally had the sister I’d always dreamed of, the revelation was life-changing. It confirmed Mum had an affair with Alana’s dad around the time of my conception.

With Mum’s passing, and Alana’s dad having been tragically killed in a motorbike accident when we were bubs, we were left with questions forever unanswered

Did they feel guilty keeping their secret? Did Mum ever want to tell me the truth? I wanted to ask.

But sadly, I’d never get the chance.

two girls smiling — Alana and Casey in 1997. Credit – Supplied

READ MORE: DNA shock: 59-year-old man discovers he has a secret family

Flicking through an old family photo album, I couldn’t help but spot my smile on my uncle’s face.

‘It’s uncanny,’ I realised, matching my smile with Alana’s too.

You two are definitely sisters! followers agreed, commenting on my videos.

While I still can’t believe Alana, 35, turned out to be my secret sister, and we no longer live next door to one another, our bond has grown tenfold.

When we’re not chatting on FaceTime, we’re spending our weekends together at the park with Alana’s three children, or whipping up something together in the kitchen.

As for the man who raised me, this journey has only brought us closer together. I know I can always count on Dad to be there when I need him.

I always loved Alana like a sister, now we have the results to prove it!