Reports at the time suggested that it was because Rob, 27, was growing increasingly uncomfortable with his weight and now Kim, 33, has confirmed this.
Reality star Kim also insisted she was totally fine with Rob’s decision not to attend her and 37-year-old Kanye’s nuptials.
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Speaking on Watch What Happens Live, Kim said: “He sent me a long email the morning [of the wedding], that he was going to leave. There was no fight.
“I just thought, ‘You know what, this is my day, I’m not even going to worry about it.”
Kim admitted that, despite understanding that Rob was feeling very self-conscious, she hopes that his weight won’t make him miss out on more family activities.
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She also said that she gets ‘frustrated’ when she feels like Rob isn’t trying to change the things he’s not happy about.
“My brother and I are so close, he’s one of my best friends. I’m definitely a tough love kind of person,” she added.
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“If I don’t like something that’s going on in my life, I change it, and I don’t sit around complaining about it for a year.
“I try to encourage him. And once you don’t make that change for so long, and it’s not happening, I get frustrated. My patience runs out.”