"This morning I lost my world and the world's most special woman," Lovato wrote. "I miss her more than words can even describe. There is an emptiness in my heart that only her spirit can fill and I pray that I will feel her by my side every single day until we meet again.

"She was my great-grandmother but we were so close that I never knew it was possible that anyone could have the bond that we shared even 70 years apart," she shared. "The pain I feel is almost unbearable but because of her strength I will power through it."

The pop star's great-grandfather died last year, and an uncle passed away this year.