Sia is a grandmother to two babies

She said: "My youngest son just had two babies. I'm just immediately horrified. No, I'm cool. They call me 'Nana.' I'm trying to get them to call me 'Lovey,' like Kris [Jenner]. I'm like, 'Call me Lovey.'"

The 44-year-old singer admits the 18-year-old boys had been on a "pretty massive rollercoaster" in their short lives, including being in "18 different locations" in their 18 years of life.

She added: "They were ageing out of the care system. They have until they're 21, but they were both 18 when I adopted them. I'm a little bit jaded now after investigating the foster system as much as I have done in the last year. It's failing us. Not in my experience, in my sons' experience. They've been in 18 different locations in their 18 years. Started out as a pretty massive rollercoaster. They told me one thing, I discovered another. But I just stayed really like a kind of Al-Anon Ninja. I just kept really strong boundaries."

And Sia explained what it was like parenting two older sons.

Speaking on Zane Lowe's Apple Music show, she said: "I would say, 'You could do this, or you could go back to where you came from,' which is not a nice life. It's not a good life, and I'd say, 'I'm doing this because I'm your mother. I love you. I have no other agenda other than the fact that I love you. I don't want to see you in prison. I don't want to see you as that five percent that's in prison.'"