Los Angeles (CNN) -- Robin Thicke's summertime hit "Blurred Lines" is an illegal rip-off of Marvin Gaye's "Got to Give It Up," Gaye's children claim in court documents filed Wednesday.
Fans, journalists and music experts immediately recognized similarities between Gaye's 1977 hit and the 2013's summertime smash, Gaye's heirs contend.
The controversy is a high-stakes legal fight involving an alleged conflict of interest with Sony-ATV, the music publisher half-owned by Michael Jackson's estate.
Gaye's heirs not only accuse Thicke and "Blurred Lines" co-writers Pharrell Williams and "T.I." Clifford Harris Jr. of copying Gaye's song, but they also contend Sony-ATV failed to meet its responsibility to protect the copyright.
The Gaye family contracted with Sony-ATV after the singer-songwriter's death to administer his music catalog, but it also represents Williams' songs, according to a counterclaim filed Wednesday in response to a lawsuit filed by Thicke, Williams and Harris.
The publisher, however, refused to sue the "Blurred Lines" writers when the family asked them to do so, the Gaye's lawyer said. As a result they "reluctantly" included Sony-ATV as a defendant in their counterclaim, he said.
The "Blurred Lines" writers filed their pre-emptive lawsuit in August asking a federal judge to declare that their song was not a copyright infringement on Gaye's work amid public rumblings about the similarities.
Thicke's inital lawsuit contends there are "no similarities" between his song and Gaye's "other than commonplace musical elements"
"Being reminiscent of a 'sound' is not copyright infringement," his complaint argues.
The Gaye family counterclaim includes Thicke quotes from an interview with Billboard Magazine published in July.
"Pharrell and I were in the studio making a couple records, and then on the third day I told him I wanted to do something kinda like Marvin Gaye's 'Got To Give It Up,' that kind of feel 'cause it's one of my favorite songs of all time," Thicke reportedly said. "So he started messing with some drums and then he started going 'hey, hey, hey' and about an hour and a half later we had the whole record finished."
The filing also quotes what music journalist wrote about the two songs.
New York Times writer Rob Hoerburger: "And that bass line came right from Marvin Gaye's No. 1 hit from the summer of '77, 'Got to Give It Up'."
Rolling Stone magazine contributor David Ritz: "When I first heard Robin Thicke's 'Blurred Lines,' my reaction was the same as millions of other R&B fans: Hey, that's Marvin Gaye's 'Got to Give It Up.' "
Vice magazine music critic Paul Cantor: "You probably don't feel guilty for liking 'Blurred Lines.' Maybe that's because it was originally a Marvin Gaye song ("Got To Give It Up") and Marvin Gaye is ... awesome."
The filing by the heirs also includes a report from musicologist Judith Finell, who identified a "constellation of at least eight substantially similar compositional features between the two works."
"The signature phrase, vocal hook, backup vocal hook, their variations, and the keyboard and bass lines" are substantially similar and they share "departures from convention such as the unusual cowbell instrumentation, omission of guitar and use of male falsetto," it said.
Gaye's heirs also accuse Thicke of stealing from their father's 1976 hit "After the Dance" when he recorded "Love After War" in 2011. Those tunes "contain substantially similar compositional material in their choruses, including the melodies of their hooks," the Gaye filing contends.
The family suggests that Thicke has a "Marvin Gaye fixation."
"Blurred Lines" stayed at the top of Billboard's pop chart for a record 16 weeks this summer and sold more than 6 million copies, according to court documents.
CNN's Denise Quan contributed to this report.