Demi Lovato has spoken of her admiration for her sister.

The singer took to Instagram on Sunday (December 28) to gush with pride for her younger sibling Madison.

Posting alongside a photo of the girl, Lovato said:

"Damn... My little sister @Madisontheaerialist is officially a teenager today. I couldn't be more proud of her with what an amazing person she's become.

"So intelligent, so talented, so funny, so beautiful and so bad ass. Literally the coolest little sister anyone could ever have. I love you Mad...You'll always be my baby girl...#HappyBirthdayMaddie."

The US star meanwhile won the Best Live Session Cover award in Capital FM's 2014 fan vote recently.

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Watch Demi Lovato being interviewed below: