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. '' Â . Who owns happy birthday ? Lawsuit seeks return of millions . 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 do n'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 . 'To Kill a Mockingbird ' novelist sues over trademark . CNN 's Denise Quan contributed to this report .
Gaye family also contends Thicke 's ` ` Love After War '' copied Gaye 's ` ` After the War '' . Thicke , Otis Williams and Big Mr . recorded the summer smash . Musicologist has identified eight similarities in the two songs , counterclaims says . Family suggest Thicke has ` ` Marvin Gaye fixation ''