Cousins Lily Allen, Sam Smith at Splendour

Pop star Lily Allen will have a chance to swap family gossip with her cousin, singer Sam Smith, when they both play at the Splendour in the Grass festival in Byron Bay this weekend.

Smith, whose single Stay With Me is currently at No.13 in the ARIA singles charts, recently revealed how stunned he was when Allen confirmed they are related.

Earlier this year, Smith sent Allen a Tweet informing her that his parents were adamant he is a cousin of hers.

"She's my cousin but I've only met her once in my entire life. My family told me for years that she's my cousin.

"I never believed them so I tweeted her and she tweeted me back saying that we are cousins."

Both Smith and Allen are on Sunday's Splendour in the Grass bill, so they will have a chance to catch up on their family tales backstage.

Allen landed in Melbourne on Wednesday morning, ahead of her Splendour appearances and sideshows in Melbourne and Sydney.

The singer was clearly feeling the effects of the long journey, tweeting "Next level jet lag" after landing at Tullamariine Airport.

Before that, she had tweeted a map of Australia with "You next" alongside the hashtag "#10gigsin2weeks".

She will perform just three gigs in Australia before she heads to the US to perform with Miley Cyrus.