Demi Lovato's Estranged Father Patrick Lovato Passes Away, 'Heart Attack' Singer's Sister Tweets 'Rest in Peace Daddy I Love You'

Demi Lovato's biological father Patrick Lovato has passed away.

The news of his death was announced Saturday evening when Demi's sister, Dallas Lovato, tweeted "Rest in peace daddy I love you.." Patrick reportedly died of a heart attack on June 22, according to US Weekly.

Patrick Lovato has battled cancer in the past.

Demi and her dad had a difficult relationship. The "Heart Attack" singer and her father have been estranged since 2007. Her parents got divorced in 1994.

Despite the strained relationship, which has included Patrick speaking out about Demi's life and the troubles of young stardom, Demi missed X Factor auditions and a photo shoot in order to grieve and be with her family.

Her co-judge Simon Cowell sent out a message of support to Demi. "My thoughts are with you Demi. X," he tweeted.

Though Demi was quiet over the weekend about the passing of her biological father, the singer sent out a vague message of thanks to her 15 million Twitter followers. "I feel so humbled to have had so much support from my fans, friends, family and complete strangers.. God bless you all, thank you so much," she stated.

Demi addressed the difficult relationship with her father in her song "For the Love of a Daughter" off her 2011 album Unbroken.

"Your selfish hands always expecting more, / Am I your child or just a charity ward? / You have a hollowed heart, / But it's heavy in your chest... Put the bottle down, / For the love of a daughter," she sang on the track, hinting at some of the issues in their relationship.