The only Kardashian brother jetted home to Los Angeles on Saturday just as older sister Kim and rapper Kanye West were exchanging vows in Italy.
Rob has yet to explain his mystery absence but did return to Twitter overnight to send a birthday message to Scott, who is in a long-term relationship with Kourtney.
"Happy Birthday @ScottDisick! Love You Brother!" he wrote.
Is he deliberately avoiding answering the question we all really want an answer to?! Does Rob's message mean there was no massive family bust-up in Europe as has been reported?
As Rob hasn't explained his absence from the wedding, the rumour mill is flying, with everything from a huge family argument to concerns over his weight gain being touted as reasons.
Other unconfirmed reports say Kim was annoyed Rob hadn't addressed his weight issues ahead of the wedding, causing a row. But neither Rob nor Kim has said this is true.
A source told People: "He is really overweight and having a hard time with it. There was no big fight between him and Kim. This was just a decision he made."
Rob addressed his weight gain in a flurry of tweets sent ahead of Kim's wedding, denying he was seeking help at 'fat camp' and saying he'd deal with his size when he was ready.
"First, I don't believe in rehab or therapy or anything of that sort, and second, I'm a grown man and will work on myself when I choose," he said. "I'm aware that I'm fat that def aint a surprise to me lol and my only therapy will be in the gym anyways had to say somethingggggggggg."
While Rob jetted home early, the rest of the Kardashian-Jenner clan were on hand to watch Kim and Kanye become man and wife at the Fort Belvedere in Florence on 24 May.
After the nuptials, the couple flew by private jet to Cork, Ireland for their wedding. Their daughter North, who turns one in June, returned to LA with grandmother Kris Jenner.
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