Ant McPartlin has said Father Dermott Donnelly was the "kindest, wisest man I knew" and will "never be forgotten" following his death at the age of 55.
McPartlin, 46, wrote on Twitter: "Fr Dermott you were the kindest, wisest man I knew. Rest in peace my friend. You will never be forgotten.
"My thoughts, prayers and love are with your wonderful family. The world has lost a special man. X A."
The diocese of Hexham and Newcastle was the first to announce the news of Father Dermott's death on Friday afternoon - with Declan, 46, paying tribute to his brother shortly afterwards.
He wrote on Twitter: "I am heartbroken to tell you that my darling brother Fr Dermott, @TweeterPriest, sadly passed away this afternoon.
"We are all beyond devastated.
"Thank you for your messages of sympathy and support, they are appreciated DD."
In 2015, Father Dermott officiated at the wedding of his brother to Ali Astall in Newcastle in a star-studded ceremony.
A statement from Hexham and Newcastle diocese said: "It is with great sadness that we have to inform you of the death of Fr Dermott Donnelly, who died peacefully this afternoon in hospital.
"This has come as a great shock to all of us.
"Please pray for the repose of his soul and keep his family, especially his mother, in your prayers at this difficult time."
Father Dermott recently celebrated his 30th anniversary of service to his parish and community, where he was best known for his work with young people and youth ministry.
He was a member of the clergy for St Joseph's Church in Stanley, County Durham.