Fear of his father couldn't keep Kim Jong Il from Sung Hae Rim. He was completely besotted with her. He was a film buff, passionate about the movies, and she was a beautiful and famous star of North Korean cinema. The two had become "pals," says Sung, through this mutual interest.
Meanwhile, the actress saw the match partly as a way to lift political pressure from her own family. Her father was a wealthy South Korean landowner who sympathized with the Communists and moved north. In spite of that sacrifice, he was persecuted in his adopted country as a member of an enemy class. But politics was just one part of the actress's calculations, says Sung. Her sister was genuinely fond of Kim Jong Il and felt sorry for him because he grew up without his own mother.
If it weren't for his father's potential disapproval, Sung Hae Rang believes, the match might have proved much happier. "If circumstances had been different," she wrote in her memoir, "they could've made a great couple." Instead, no one outside a tiny circle knew they were partners until after his father died and was succeeded by Kim.
http://www.time.com/time/asia/covers/501030630/story.html
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“If it weren't for his father's potential disapproval,” definitely is referring to the past situation.
Then, doesn’t have to be ““If it had not been for”, as in "If circumstances had been different,", because all the grammar books are saying that "if it were not for" refers to the present, and "if it had not been for" refers to the past situation?