Panettiere met Klitschko, who was was 13 years older than her, at a party in Los Angeles when she was 19.
After their daughter was born, the actress was hit hard by postpartum depression and was drinking heavily.
Klitschko helped get her treatment but when their daughter was three, he asked her to sign over custody.
Panettiere reluctantly agreed and wrote in her autobiography, which was published earlier this year: “Not being under the same roof with her every day has been the most gut-wrenching experience of my life, and it’s hard to describe the layers of emotion, including sadness, resentment, and anger I felt because of it…
“I grieve that I’m not the mother I thought I’d be, and definitely not the mother I want to be. Trust me, no one should ever have to raise a child on FaceTime.”
She remained involved in her daughter’s life and added that “despite it all, the bond I have with Kaya is incredibly strong”.