It's AvrilLavigne's 40th birthday ... Avril started dating Sum 41 lead singer DeryckWhibley when she was 19 years old and he was 23, after they became friends when she was 17.
This rules! AvrilLavigne brought out her ex-husband, Sum 41 frontman DeryckWhibley, to play In Too Deep as part of her Greatest Hits tour in Las Vegas over the weekend.