Warner and King, both 42, dated for more than two years and shared a house until he asked her and her 17-year-old son to move out, Us Weekly said Thursday. The magazine said he had lost feelings for her and that King was brokenhearted by the breakup.
The two had been friends since they were TV child stars in the 1980s, with Warner portraying son Theo Huxtable on NBC's long-running sitcom hit "The Cosby Show" and King playing teenager Brenda Jenkins on the same network's Marla Gibbs sitcom, "227."
After beginning a romance with her longtime friend, King told Parade magazine, "I believe the universe has a plan, and we probably wouldn't have been ready years ago. We both had to do whatever we had to do to be ready for each other now."
They fended off engagement rumors in 2011, with King confirming to "Access Hollywood" at the time, "No, we're not engaged."
The actress -- whose films include "Jerry Maguire," as the wife of Cuba Gooding Jr.'s character -- was married to music industry executive Ian Alexander Sr., with whom she had son Ian Jr. in 1996. The couple divorced in 2006.
Warner had been in a relationship with Michelle Thomas, who played Theo's girlfriend Justine Phillips on "Cosby" and also co-starred on "Family Matters." They were together when she died of a rare form of cancer in December 1998.
He later was involved with "A Different World" actress Karen Malina White, shooting down rumors of marriage in 2009, telling Essence magazine, "I'm not married. People probably started saying that because we were [in a relationship] for seven-and-a-half years."