Billie Eilish has started writing her third album with her brother Finneas O'Connell.

The 19-year-old singer released her second record 'Happier Than Ever' over summer, and now her sibling and collaborator - who dropped his own debut LP 'Optimist' in October - has confirmed they are working on the follow-up.

Speaking to Rolling Stone magazine, he said they were "really excited to start working on" new material, and noted while the duo have "interesting skeletons" for new tracks, they are "not sure what animals they are".

He added: "We’ve got the net in the ocean, and we’re picking up detritus.

“And then you sift through all that, and you pick out the treasure, and then you have an album. I’m really excited. I think we’ve got a lot to say.”

However, Finneas dimissed the idea of Billie dropping her third album in 2022, noting that their focus is on her 'Happier Than Ever' world tour, which starts in February.

He explained: "This tour is this album. We’ve played some festivals, but we haven’t done Billie headliner solo shows, and we’re really excited to play 'Happier Than Ever' on the road.

"So even if it’s in the can by February, we’ll [delay it] for a little bit. Because I like letting projects breathe…

“You don’t want to step on the toes of an album like that. You make your stuff mean less, I think, when you do that.”

The singer-songwriter and producer previously revealed that their musical talent is something of a family affair which started as a parental influence.

He said: "Our mum is a really talented songwriter so she taught us the basics of song writing and it was just this lightbulb moment for me where I was like, ‘Oh man, I love doing this so much.' "