Simon opened up about his close friendship with Lee in a candid blog post this week, in which he credits his bandmate for encouraging him to join Blue and achieve his dreams.
The pair first met at a modelling competition in the 90s, when Simon was living in Manchester and struggling to figure out what career path to take.
Over a year later and following the death of his grandfather, Simon reconnected with Lee and decided to take a leap of faith by moving in with him in London.
"I didn't know this boy well but he had it in his heart to look after me when I had nobody else in London," Simon wrote in his blog for the Metro. "I didn't know where my life was leading and when I got to London it was so hard. Lee was always the one that helped me to forget my problems."
The two singers soon formed a tight bond and auditioned for Blue together - something that Simon will always be grateful to Lee for.
He added: "To this day I still owe him my life and I will support him forever. The Lee I know is my saviour... He'll always be the guy that saved me."
Simon and Lee, along with bandmates Duncan James and Antony Costa have enjoyed a long career as part of Blue.
Last year, the group released their fourth studio album, Roulette, and also joined ITV series The Big Reunion, embarking on a successful UK tour with fellow bands including Atomic Kittem, Liberty X and 5ive.
This month however, Blue have gone the extra mile to prove how close they are by rallying round to show support for Lee as he competes on Celebrity Big Brother.
The 30-year-old singer has caused quite a stir since entering the CBB house and becoming embroiled in a love triangle between housemates Casey Batchelor and Jasmine Waltz.
His questionable actions with the two women, as well as his risqué pole dancing and emotional breakdowns in the diary room have caused Simon, Duncan and Antony to jump to his defence on a number of occasions.
Yesterday (20 January), Duncan wrote on his blog: "I really hope that viewers recognise that [Lee] is talented and that he has overcome all sorts to be the man that fans and family love today.
"Once Lee is out of the house he can speak for himself and have his own voice..."
Last week, Duncan even had dinner with Lee's love interest Jasmine after her eviction from the house, in a bid to get to know the American actress better and find out whether she was a good match for his mate.
What do you think of Lee Ryan on Celebrity Big Brother? Let us know below, as the best comment from across the website each week wins £50!
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