Liam shared in an interview that Chris did not tell them in advance and kept it as a surprise, reported Huffington Post.
Chris called their father to tell him to look at his bank account.
"He [his father] called my brother Chris back and said, 'I don't know how to feel. Since I left home I have had debts and I thought I'd be paying them off until I died and have this weight hanging over me, and now to have them completely cleared.'
Liam is an ambassador for the Australian Childhood Foundation, along with his big brother.
Their parents worked with the organisation to support children going through trauma, and now Liam and Chris are using their celebrity status to give the campaign an extra boost of star power.
"If you want to be a good person who adds to society, you have responsibility. That is something I take very seriously," Liam said.