Ed Sheeran is being sued over claims he copied the core elements of Marvin Gaye classic Let’s Get It On.
According to the lawsuit, Sheeran lifted the "heart" out of the 1973 track for his hit song Thinking Out Loud.
The heirs of Ed Townsend, who co-wrote Let's Get It On with Gaye, have filed the copyright motion and asked for damages to be assessed at a jury trial.
They claim the harmonic progressions, melodic and rhythmic elements central to Let's Get It On formed the structure of Sheeran's track.
Thinking Out Loud topped the UK chart in November 2014 and later became the first song to spend a full year in the Top 40.
It won Sheeran two Grammy awards and has been viewed more than 1.2 billion times on YouTube.
The lawsuit states: "The defendants copied the 'heart' of 'Let's' and repeated it continuously throughout 'Thinking'.
"The melodic, harmonic, and rhythmic compositions of 'Thinking' are substantially and/or strikingly similar to the drum composition of 'Let's.'"
Sheeran, Sony/ATV Music Publishing and Atlantic Records have not commented on the legal motion.
The lawsuit comes two months after musicians Martin Harrington and Thomas Leonard sued Sheeran for $20m (£15.3m) over his hit song Photograph.
Harrington and Leonard claim the track has a similar structure to their song, Amazing.
Gaye's family last year successfully sued Robin Thicke and Pharrell Williams for copyright infringement over hit song Blurred Lines.
Thicke and Williams were ordered to pay Gaye's three children $7.4m (£5.6m).