Riley Keough penned a heartfelt tribute to her late brother Benjamin Keough, who died by suicide earlier this week.

Lisa Marie Presley's 31-year-old daughter posted a series of throwback photos with Benjamin on Instagram early Saturday.

"Mornings are the hardest. I forget you're gone. I can't cry because of the fear that I will never stop. A pain that's new to me," Riley wrote.

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The actress described Benjamin as an "angel" and "pure light," and called him her "baby brother" and "best friend."

"Wild man. Intellectual. Witness to my life. Twin soul. Protector. Too sensitive for this harsh world," she continued.

Riley went on to say she hopes Benjamin can give her "strength to eat," adding that she hopes "you feel god."

"I can't believe you've left me. Not you sweet Ben Ben. Anyone but you. I guess this is true heartbreak. I hope we meet again," her emotional caption concluded.

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Benjamin, the son of Lisa Marie, 52, and musician Danny Keough, died by an "intraoral shotgun wound" and his manner of death was ruled a suicide by the Los Angeles County Medical Examiner. He was 27.

Benjamin Keough died at age 27 by suicide.

Benjamin Keough died at age 27 by suicide. (Dave M. Benett/Getty Images)

He was also the grandson of Elvis and Priscilla Presley.

Lisa Marie reacted to her son's death in a statement via her manager on Sunday.

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"She is completely heartbroken, inconsolable and beyond devastated but trying to stay strong for her 11-year-old twins and her oldest daughter Riley," said the statement. "She adored that boy. He was the love of her life."

Compared to some of his family members, Benjamin lived a relatively spotlight-free life. He has one acting credit on IMDb, and TMZ reported that he had a $5 million record deal in 2009.

He was also known for his striking resemblance to Elvis, which, according to the outlet, Presley once addressed.

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"Ben does look so much like Elvis. He was at the Opry and was the quiet storm behind the stage," she said. "Everybody turned around and looked when he was over there. Everybody was grabbing him for a photo because it is just uncanny."

Fox News' Nate Day contributed to this report.