Centre Dey, 27, and hooker Kelly, 25, both played in the same school team at Stewart's Melville College before signing professional contracts with Edinburgh in the summer of 2003.
Now five years on Dey admits he is delighted to have agreed a one-year deal to extend his stay at Edinburgh and has tipped the team to build on the achievements of the 2007/2008 season.
Dey said: "I have played all my professional rugby with Edinburgh and I'm very proud to be given an opportunity to continue doing that.
"We have enjoyed a good season and the set-up bodes well for the future. I'm very excited to be a part of that.
"I guess looking back at our school side, we always knew we had a good team and Ned (Kelly) and I have been the fortunate two that have been able to go on and play professionally.
"It has been good to have played alongside him for so many years and I have been lucky to have made lots of long-term friendships during my time at Edinburgh.
"I am fortunate to be playing rugby alongside my mates, who I get on with both on and off the pitch.
"I think that factor has been instrumental behind what we have achieved this year and will stand us in good stead going forward as well. We work hard for each other and that counts for a lot."
Scotland 'A' internationalist Kelly has signed a two-year deal and admits it is slightly bizarre that he is still lining up alongside Dey 11 years since they first played together at school.
Kelly said: "I suppose to train with someone every day that you went to school with is a bit strange. Matt was a year above me at school, but we started playing together when I was in the fourth year and he was in the fifth year.
"But it is good to have shared so many experiences with Matt at Edinburgh and I'm really looking forward to that continuing next season."
Edinburgh-born Kelly revealed he has developed a strong affinity for the club over the past five years and understands what the team means to the people of his hometown.
He added: "It means a lot to me to play for Edinburgh because you want to win for the club and also for the city.
"There are a lot of people I know in the city who are always looking to see how the team is getting on, so it is good to be able to do it for them as well."
Kelly also believes the future looks bright at Edinburgh and attributes that to the input of head coach Andy Robinson, who took charge of the team in October.
He said: "That was definitely the best season I've ever experienced at Edinburgh. The guys really did well and they have responded well to Andy; Edinburgh is a good place to be."
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