The 30-year-old, who was diagnosed with the neurological disease in 2012, marked World MS Day on Wednesday (25May16) by penning a heartfelt open letter, sharing his experiences of living with MS.

In his missive, the reality TV star thanked his family for helping him come to terms with his diagnosis, writing, "After I was diagnosed, I turned to my family first, and then to the Internet. I tried to gather as much information as I possibly could on what MS is, how it manifests and what that would mean for me. I was overwhelmed, and it was a lot to process and digest.

"My family was an incredible support system for me, helping me understand and wrap my head around the disease, and to them I am forever grateful."

In the wake of Jack's diagnosis his father, Black Sabbath rocker Ozzy Osbourne, 67, told Britain's Hello! magazine, "If it was me, you'd think, 'Ozzy had a reputation and it caught up with him', but Jack is such a good guy."

On Twitter, his sister Kelly, 31, asked fans to, "support my brother in not only his bravery but honesty!" adding, "I love you so much jack & I'm so proud of you!"

His mother Sharon, 63, has also been vocal in helping her son raise money and awareness for MS charities, with Jack launching his own campaign last year (15).

In his open letter, published by America's People magazine, Jack insists World MS Day is also an opportunity to celebrate the work of those who care for sufferers, adding his wife Lisa, 29, and their children Pearl, four, and 10-month-old Andy gave him the courage to fight the disease.

"In my eyes, World MS Day is just as much about our family and friends as it is about everyone living with MS," he explains. "It's not just individuals who can suffer. My wife and kids are my reason for wanting to endure whatever this disease throws at me."

The star went on to thank Lisa and the rest of his family for their support, adding, "So to all my family and friends who had supported me and been there for me, I'd like to say thank you, I love you. This day is for you as well."