Two Californian musicians are suing British singer-songwriter Ed Sheeran for $20-million (almost R300-million) over his hit song Photograph, which they claim bears a similar structure to one of their songs, according to court documents.The copyright infringement lawsuit was filed by Martin Harrington, a songwriter and producer, and Thomas Leonard, a songwriter signed to Harrington's company HaloSongs, in a federal court in the Central District of California.The two musicians allege Sheeran's ballad, Photograph, released as a single last year, has the same musical composition to their song, Amazing, which they said they wrote in 2009.Other named defendants include Snow Patrol's Johnny McDaid, credited as a co-writer of Photograph.In documents that include musical note comparison and chord breakdowns of the two songs, Harrington and Leonard claim the chorus of Photograph shares 39 identical notes with Amazing. The documents say that Photograph has sold more than 3.5 million copies worldwide, and most recently was featured in the romantic drama Me Before You.Grammy-winning Sheeran, 25, has become one of the UK's top-selling artists in the past two years, and has written and co-written tracks for artists such as One Direction, Taylor Swift and Justin Bieber.Harrington and Leonard have also written songs for Kylie Minogue and Emma Bunton. ..