Demi Lovato and Nick Jonas: The Unexpected Duet

Demi Lovato is apparently not one to hold grudges.

The singer - who opens up about her battles with cutting and depression in the latest Self - may have once dated Joe Jonas, but that didn't stop her from inviting his brother on stage with her for a concert in Los Angeles this week.

Nick Jonas took fans by total surprise when he walked out to play guitar while Lovato sang the lyrics to "Catch Me" and "Don't Forget." Those in attendance said Nick even mouthed "I love you" when he walked off stage. AWWWW!

Watch this duo perform now:

Demi Lovato and Nick Jonas: "Don't Forget/Catch Me"