The 26-year-old singer - who wrote the song 'Pretty Woman' for Robbie's 2016 album 'The Heavy Entertainment Show' - believes his career is extremely similar to that of the former Take That star and he has developed a ''little obsession''.
He told The Sun: ''I feel a weird affinity with Robbie. We email now and then but I've been reading up on him and his career is so similar to mine.
''Like the way the album's going, the way it went to stadiums, the way it was just like one lone man... a very lonely sort of life. I have a little obsession with him and working out how he did stuff.''
While Ed admitted life on the road as a solo star can be lonely, he has invited some of his old schoolmates, who he sang about on the song 'Castle on the Hill', to join him on tour.
He explained: ''I've had three mates on tour with me and next year I've got four, who are my schoolmates. They are all the 'Castle on the Hill' people.
''I don't have a band and all of my team, God bless them, are married with kids so don't want to f***ing go out in Tokyo at two o'clock in the morning.''
Recently Hollywood actor Hugh Jackman praised Ed for his personal lyrics but wondered how his friends feel about their lives being laid bare in his music.
He said: ''I don't think there is anyone better than Ed Sheeran at telling a story. I listen to Ed Sheeran all the time. 'Castle on the Hill' really moves me and I think it's beautifully done. Not only does it tell his story but he is quite open about his friends.''
And the 49-year-old actor - who has children Oscar, 17, and Ava, 12, with wife Deborra-Lee Furness - thinks Ed probably ran the lyrics by his childhood pals before including them in the song because it is so easy to identify who he is singing about.
He added: '' I was just thinking about it yesterday when I was on the rowing machine, I thought I wonder if he rang them and said hey are you cool with these lyrics? Everyone in the town is gonna know who they are talking about and actually I thought, I bet he did ring them and I bet they are all okay because in the end he does it with such affection.''
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