Katherine Langford is one of Australia's biggest stars after finding fame on Netflix's 13 Reasons Why in 2017, thanks to its cult following.

And her younger sister, Josephine Langford, 20, looks set to follow in her footsteps after landing the lead role in upcoming and highly-anticipated teen movie, After.

But the Perth-born pair have left their fans baffled after failing to reference each other in interviews, share any photos together or even follow each other online.

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Family feud? 13 Reasons Why star Katherine Langford, 22, (pictured) and actress sister Josephine, 20, baffle fans as the Aussie siblings fail to reference each other since both finding fame

During a chat with the Sydney Morning Herald in 2017, Katherine, 22, reportedly wouldn't discuss her family when the publication approached the subject.

The newspaper wrote: 'She reveals she has a 19-year-old sister, but shies away from providing any more detail on her family.'

In another interview with L'Official in May, Katherine denied any of her family were involved in the industry - despite Josephine already having acted in several things.

'Nobody in my family is in show business': Katherine denied having any famous family in May, despite Josephine (pictured), having already starred in several TV and film projects

Leading lady: Katherine shot to fame in 2017 as the lead on Netflix show 13 Reasons Why (pictured), and Josephine is tipped to soon have her breakthrough role in teen movie After

Big mystery: Katherine reportedly 'shied away' from discussing family while promoting the popular program with the Sydney Morning Herald last year

While talking about her upbringing to the publication, Katherine reportedly said: 'Nobody in my family is in show business.'

Confused at the failure to acknowledge Josephine, one fan wrote on Twitter: 'I find it weird that Katherine and Josephine don't follow each other on Instagram.'

Another follower of the famous family recently said: 'Any Katherine Langford fans tell me if she has beef with Josephine? They don't follow on Instagram and they don't even have any pictures together.'

A third fan questioned: 'Josephine and Katherine Langford are sisters but they don't follow each other on Instagram?'

With many debating if the siblings are close, some fans believe they are simply fiercely private when it comes to their personal lives.

Her star is rising: Josephine hit the carpet at Variety's 2018 Power of Young Hollywood event in LA on August 28 after wrapping movie, After, earlier in the month

Confused: Fans have expression their confusion on social media at the fact the sisters have seemingly never publicly mentioned or shared any photographs together

'I find it weird': The siblings also don't follow each other on Instagram

Going global: Fans all around the world have questioned their relationship, with some simply suggesting they are both fiercely private about their family

Josephine hit the carpet at Variety's 2018 Power of Young Hollywood event in LA on August 28 after wrapping movie, After, earlier in the month.

The beauty has previously starred in supernatural horror film Wish Upon and Australian TV series Wolf Creek - but this look sets to be her big breakthrough role.

Daily Mail Australia have contacted both Katherine's management and Josephine for comment.