Kelly Osbourne Drunken Relapse Due to Brother Jack's MS Diagnosis?

Kelly Osbourne recently suffered a drunken relapse after almost three years of sobriety and critics suspect that her brother Jack Osbourne's MS diagnosis may be the cause.

Jack, 26, was diagnosed with relapsing remitting multiple sclerosis in early June and his sister Kelly is said to be struggling with the news. On June 19 she boarded a flight from LAX to Atlanta where onlookers witnessed her drunken behavior, according to Star Magazine.

"I saw a flight attendant bring alcoholic beverages over to Kelly's section in First Class at least four or five times," an eyewitness told Star.

"And when we landed just after midnight, her assistant, who flew with her, had to help her off the plane. They were the last to leave. There was already a burly security guard waiting for them at the arrivals lounge," the source added.

Kelly, who has battled addiction for years, was described as being evidently drunk. The 27-year-old was so intoxicated that she needed assistance walking.

"Kelly's hair was hanging down, she was mumbling and her makeup was a mess. The guard and her assistant supported her under each arm and basically carried her down the corridor to the airport tram, with Kelly swaying from side to side. I felt so sorry for her," the source explained.

Jack has experienced symptoms of MS for several years, including partial blindness, numbness in his legs, and bladder, bowel and stomach problems.

He recently opened up about the anger that he felt while waiting for his final test results, and says that he remains confident that he will be ok.

"Then I got really sad for about two days and, after that, I realized being angry and upset is not going to do anything – it's only going to make it worse. 'Adapt and overcom' is my new motto," Jack told Hello Magazine.

Kelly immediately took to Twitter after the drinking incident, where she appeared to be embarrassed by her behavior.

"Had a nerves breakdown yesterday that was cool! #Not." Kelly tweeted.

Kelly is expected to pull through despite the challenging time in her life, and the source described her as being "tough as nails."

"She always lands on her feet. She's had so much to deal with at a young age, and she's tried to handle it the best she can. I wouldn't be surprised at all if the sudden sad news about Jack helped push her into a dark place again. But she'll come through it OK," the source said.