In a statement, he said: "She's now with Carrie and we're all heartbroken."
"She said, 'I want to be with Carrie'," he added. "And then she was gone."
The 84-year-old Singin' In The Rain star died on Wednesday, barely a day after daughter Carrie.
It's reported she suffered a stroke and emergency services were called at 1pm local time on Wednesday to her son's Beverly Hills home, where they were making plans for Fisher's funeral.
Tributes for Reynolds and Fisher have poured in from around the world.
Dame Joan Collins tweeted: "Truly heartbroken to hear @DebbieReynolds1 has died. She was a wonderfully warm friend and colleague. Praying for Todd & Billie. #RIPDebbie."
William Shatner wrote: "Debbie Reynolds was one of the last of Hollywood Royalty. It breaks my heart that she is gone. I'd hoped that my grieving was done for 2016."
His fellow Star Trek actor George Takei added: "There is nothing harder than having to bury a child. Debbie died of a broken heart, but she's with her daughter now."
Debbie Reynolds had posted on Facebook earlier in the day her thanks to those who had prayed during Carrie Fisher's short illness.
She wrote: "Thank you to everyone who has embraced the gifts and talents of my beloved and amazing daughter.
"I am grateful for your thoughts and prayers that are now guiding her to her next stop. Love Carrie's Mother."
She leaves behind one son, Todd, who oversaw her businesses as well as working within the media.
In the 1980's he founded the Hiding Place Church after becoming ordained shortly after coming to faith.