Wladimir Klitschko is remembering Hayden Panettiere on what would have been her 37th birthday.The former heavyweight boxing champion shared an emotional tribute to his former fiancée on Aug. 21, five days after the “Nashville” actress died at 36.

“Today is Hayden’s birthday. Instead of celebrating the way we had planned, today we celebrate her life, her spirit, and the love she brought into this world,” Klitschko wrote on Instagram.

“At a time filled with so much sadness, your kindness has reminded me that there is still so much good in humanity,” he added as a thank-you to Panettiere’s fans, friends and others who have reached out to the family with messages of support.

Klitschko encouraged those reading his message to focus on love and kindness amid the grief.

“If you’re reading this, I ask just one thing: even if only for a moment, think about LOVE,” he wrote. “Reach out to a friend. Forgive someone. Be kind. Love is a superpower. Use it.”He ended the tribute with a message directly to Panettiere: “Happy Birthday, Hayden. You are loved, you are missed, and you will never be forgotten”

Panettiere died just days before she would have turned 37 on Aug. 21. She and Klitschko, 50, began dating in 2009 and had an on-again, off-again relationship before becoming engaged in 2013. They welcomed their daughter, Kaya, in 2014 before ending their relationship in 2018.Klitschko previously paid tribute to Panettiere on Aug. 18 following the news of her death, describing her as an important part of his life despite their separation and vowing to preserve her memory for their 11-year-old daughter.

“Our family is going through a time of profound shock and grief,” he wrote at the time. “To our daughter Kaya, I will always speak of her mother with respect and make sure she remembers the person she was.”Panettiere’s relationships have also received renewed attention following her death⁠, including Klitschko and her on-and-off boyfriend Brian Hickerson.

Hickerson, who was with Panettiere at the time of her death, broke his silence this week through his attorney as authorities continue to investigate the circumstances surrounding her death

An official cause of death has not been released. Police have said their preliminary investigation found no signs of foul play or suspicious circumstances.

Contributing: Josh Peter,  Liza Esquibias and KiMi Robinson, USA TODAY