People magazine first broke the story, stating that Lavigne and Kroeger sparked up a romance while they were working together on material for her new album, but chose to keep their relationship private.
A friend of Lavigne's told the publciation: "A romantic relationship blossomed as they spent time writing together.
"He makes her so happy. Both of their families could not be more excited."
Kroeger reportedly popped the question on 8th August with a 14-carat diamond engagement ring, after dating the 27-year old for just six months.
Avril has since retweeted a message from Chad's bandmates - Ryan Peake, Chad's brother Mike Kroeger and Daniel Adair, which read: "Congratulations Avril and Chad!"
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