Hilary Duff has confirmed her devastating rift with sister Haylie Duff.

The 38-year-old singer is estranged from her older sibling Haylie - who had a guest role in Hilary's breakout TV hit Lizzie McGuire - and Hilary admitted that no longer having a relationship with her sister is "the most lonely part of my existence".

Speaking on CBS Mornings, Hilary confirmed the song We Don't Talk is about Haylie and said: "It's definitely about my sister. And just absolutely the most lonely part of my existence is not having my sister in my life at the moment."

Former Disney Channel star Hilary went on to say that she has no idea what Haylie will think of the track but she wanted to include it on her new record luck… or something "because it's [her] truth."

She said: "I don't know if she'll hear it. I don't know how she'll react to it. You know, it is a really personal part of my life that doesn't get to stay personal. So I might as well say how it is for me, and that's all I'm trying to do. I'm not trying to say anything bad. It's literally just my experience -- and that's really all I feel like sharing."

Hilary's new album, luck… or something, which she wrote with husband Matthew Koma, also features a song called The Optimist, where she examines her complicated relationship with her father.

She said: "I think it's really challenging for one person to have major success in a family. In The Optimist, that's what it feels like for me. And I'm sure it has to feel like that for him. Although I'm the kid. And it's been hard to get back to a place of health.

"There's a lot of themes of abandonment on the record. And to make songs about that with [Koma] and just have him further understand kind of my scars was really nice."

And Hilary spoke about being a child star after finding fame with Lizzie McGuire in 2001 and how she struggled to find her own identity outside of the show.

She said: "I think only something that I've come to see in my thirties, once I went through my uncomfortable phase of not wanting to be associated with [Lizzie McGuire] anymore, was like, oh, it's just complicated to play a role on TV that doesn't ever grow up.

"And now I don't care at all. And I am so overwhelmingly grateful for that experience. But it was really challenging to get to a point of peace with that.

"I started to build my life and put my focus where I felt loved and seen for me."