Sia adopted both the boy in the documentary and his friend

| Credit: Michael Tran/FilmMagic

Sia knew she had to adopt her son from the moment she first saw him on television.

In the October cover story for Vogue Australia, the musician, 44, opened up about her decision to adopt two 18-year-old boys last year, sharing that the idea came about after she was watching a documentary.

"I am obsessed with reality television and documentaries, and I watched a documentary and saw my son," she said.

The "Together" singer explained that she felt an instant connection to the teenage boy after realizing he didn't have his own family. "I was like: ‘What? Like, he doesn’t have anybody. Oh my God. I’m going to find him and I’m going to be his mummy.’ And so that’s what I did," she said.

The star ended up tracking down the boy and adopted him and his friend.

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Sia first confirmed that she welcomed two sons into her family last year during a May interview with SiriusXM's The Morning Mash Up, sharing that she adopted the teenage boys when they were leaving foster care due to their age.

"I actually adopted two sons last year. They were both 18 — they're both 19 years old now," she revealed. "They were aging out of the foster-care system. Yeah, and I love them."

The singer also appeared on Good Morning America in June and gave an update on their lives together.

"They both suffered a lot, and I've been able to get them the help — I have the resources to get them the help that they needed for their early trauma," said Sia. "It's taken a year and we've had our ups and downs, but we've never been in a better place than today, in fact."

"It's a blessing for me," added the "Chandelier" hitmaker. "I think they saved me, so I'm in heaven."

The singer also expressed interest in becoming a foster parent during her Vogue Australia interview. She called being a mother "the best thing I've ever done" and that she would be open to doing it again.

“It’s one of the hardest, but I have obviously such an overflow of love that I could definitely see myself doing it again, but not for a while," she said. "The next thing I’m planning to do is foster actual infants."

Sia said she could see herself helping out babies who might not have a stable home.

"Maybe [their mother] is drug-addicted and then I could help look after them until, you know, their mum can get back on the wagon or an adoptive home is found," she said. "If I can do that then I think I’ll feel like I’m superhuman.”