The Donegal man had been receiving treatment for an aggressive brain tumour.
His death was announced on Wednesday. He played for City from 2003 to 2012, scoring 113 goals in 209 appearances for the club.
Shaun Holmes, Mr Farren's brother-in-law, said: "He was an absolute gentleman who was football crazy".
Mr Holmes added:  "He was a fighter but it was devastating for the family to watch.
"He was very much in love with my sister Terri-Louise. She is devastated. Nothing prepares you for this. They were best friends.
"Mark and Terri-Louise previously lost triplets. It was a tough journey for them.
"He would love to be remembered as a loving husband, a gentleman and a goal scorer."
Friends, footballers and politicians have been paying tribute to Farren.
They include West Bromwich Albion and Republic of Ireland winger James McClean, who played alongside him for Derry.
Derry City legend, Liam Coyle, suggested that the new stand at Brandywell stadium should be named after Mr Farren.
Farren was in the Derry teams that won the FAI Cup in 2006 and 2012, and was voted player of the year by the Professional Footballers' Association of Ireland in 2005.
He left Derry to join Irish League club Glenavon in 2013 but was forced to quit the game because of his illness.
A book of condolence is to be opened for Mark Farren, who was a striker for Derry City Football Club.