"My beautiful sweet angel. I have loved you beyond words or description from the moment I felt you in my belly," the City by the Sea actress wrote alongside a close-up photo of Leandro on a red carpet.
"You have been my joy, my heart and all that was ever pure and real in my life. I wish I was with you right now. I wish I was with you," Drena tearfully added. "I don’t know how to live without you, but I’ll try to go on and spread the love and light that you so made me feel in getting to be your mama."
"I’m so sorry @carlosmare 😢💔. Rest in Peace and Eternal Paradise my darling boy 🙏🏽💔💔💔💔💔🕊️🕊️🕊️🕊️," Drena concluded, tagging Leandro's father, artist Carlos Rodriguez.
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While he has yet to specifically address the heart-wrenching loss of his son, Carlos uploaded a black screen with no caption to his Instagram just a couple hours before Drena broke the news. The comments section has been flooded with condolences and prayers.
Drena is the eldest daughter of Robert — who shares seven children with four different women.
The 79-year-old has five adult children: Drena, 51, Raphael, 46, twins Julian and Aaron, 27, as well as Elliot, 24.
He is also a father to Helen, 11, and recently welcomed his newborn daughter, Gia, with his girlfriend, Tiffany Chen, in April.
The Godfather Part II star adopted Drena when he married her mother, Diahnne Abbott, in 1976. They later welcomed Raphael before divorcing in 1988.
Robert shares his twins with his ex-girlfriend Toukie Smith. The former flames split in 1996 after getting together the same year his marriage to Diahnne ended.
In 1997, the Taxi Driver actor tied the knot with Grace Hightower. They are parents to Elliot and Helen and finalized their divorce in 2018.