TMZ reports:
Legendary singer and songwriter, Paul Anka, tells TMZ that in 1983, he wrote a song with Michael Jackson called, "I Never Heard" and the demo of the song was recorded for Anka's duets album, "Walk a Fine Line."

Anka gave "I Never Heard" to another artist -- Safire -- who recorded it in 1990.

Paul Anka tells TMZ the people handling Michael Jackson's estate are falling over each other... apologizing for "ripping-off my song" and offering "anything you want" to make the mess go away.

John Branca, a lawyer for Jackson's people just told TMZ, "We acknowledge that Michael and Paul wrote this song together."

Michael Jackson's estate just got a partner it didn't bank on -- because we've just learned Paul Anka is now a 50% partner in the publishing rights to "This Is It."

Anka will get other profits as well, but the publishing rights are usually the big ticket item, and sources say Michael Jackson's estate has agreed Anka gets 50%.