Demi Lovato devastated over great-grandfather's death

Demi Lovato has been left "heartbroken" following the death of her great-grandfather. The 'Cool for the Summer' singer has asked fans to pray for her great-grandmother after her beloved grandparent passed away aged 88. Alongside a picture of the old man and her puppy Buddy, who passed away in July, she wrote on Instagram: "My two favorite Buddy's are now playing in Heaven. My heart is absolutely broken and I can't even begin to imagine a world without my Papa but I know one day we'll meet again and that's what keeps me going. "I hate writing this... But RIP Papa... I miss you so much already. I love you. Please keep my Mimaw in your prayers.(sic)" Earlier this summer, the 23-year-old singer had asked fans to pray for her elderly relative as he was unwell. Demi's dog Buddy - who she shared with boyfriend Wilmer Valderama - died in July after being attacked by a coyote in their backyard.