Demi Lovato marked Father's Day this year by reflecting on their "complicated" relationship with their late birth father.

The "Heart Attack" singer took to their Instagram Stories Sunday where they opened up about their "tough relationship" with dad Patrick Lovato, who died in 2013. They also encouraged others to reach out to their fathers if they can.

"Trying not to wake up sad.. Trying to stay positive. Today is always so difficult. This is for anyone else who's lost a father, can't be with their dad, didn't know their dad, or anyone who has a tough relationship with their dad," Lovato wrote. "I spent many years on this holiday wondering whether or not I should call him.. take it from me, if you can, make the call."

"Some days I regret not calling, but other days I'm proud of myself for holding my boundary because I was doing what was best for me and my mental health. It's complicated, and I wish it were different but this made me into the person I am today," they added. "Anyway my heart goes out to the people still holding their boundaries as well."

In a subsequent post, the "Skyscraper" singer shared three throwback pictures with their late father as well as snippets of their song "Butterfly."

"Your lying taught me bout honesty, honesty / Your leaving gave me my loyalty, loyalty," they wrote on one photo of Patrick carrying the singer as a baby.

Another throwback picture showed Lovato as a teen smiling as they posed next to their father. They wrote out the lyrics, "You were never really graceful / Now you're just what you're supposed to be."

Lovato also shared a selfie with their stepfather, Eddie De La Garza, along with a loving message for him. "My favorite pic of us together, just left the Baltimore aquarium *i think* one day before tour," they captioned the photo of them flashing smiles at the camera.

"To the man who raised me, I love you so much. Thank you @eddie.delgarza Happy Father's Day dad," Lovato added.

Lovato's biological dad passed away on June 22, 2013. The "Sorry Not Sorry" singer announced his passing on Twitter at the time.

"Rest in peace daddy I love you.." they tweeted.

In 2015, Lovato spoke about their conflicting feelings about the death of their father, whom they called "abusive." At the time, the singer said they were aware that he was trying his best to be a good father but was unable to due to his mental illness.

"I was very conflicted when he passed, because he was abusive," Lovato said in a video interview on their YouTube channel. "He was mean, but he wanted to be a good person. And he wanted to have his family, and when my mom married my stepdad, he still had this huge heart where he said, ‘I’m so glad that [he's] taking care of you and doing the job that I wish I could do.'"

Lovato said their father's mental illness prevented him from being able to raise a family. Following his death, they created the Lovato Treatment Scholarship Program, which helps pay for the treatment expenses of individuals struggling with addiction and mental health.

Demi Lovato

Recording artist Demi Lovato attends the Billboard Music Awards at MGM Grand Garden Arena on May 20, 2018, in Las Vegas, Nevada. Photo: Getty Images/Frazer Harrison