John Finnan was the grandfather of Carmel Finnan.
Having been born out of wedlock to a fifteen year old mother, Carmel was raised by her grandparents and only discovered her true parentage at the age of fourteen. She reacted by rebelling against her family and taking up with the neighbouring McGuire family and became obsessed with the husband Michael McGuire, even falsely claiming to be carrying his child.
After spending time in psychiatric hospital and apparently making a full recovery, Carmel began training as a nurse in England and John was grateful that she had a chance of a fresh start. In March 1993 however, he was summoned to Weatherfield as Carmel was in hospital after falling down the stairs and was accusing Gail Platt of pushing her in a jealous rage. John visited the Platts at No.8 and although they were initially reluctant to be questioned by him about Carmel's alleged dalliance with Martin, he noticed stark similarities with her previous infatuation with Michael.
John apologised to the Platts and assured them that he would get Carmel to drop the charges swiftly. He collected her from the hospital to take her back to Ireland and receive further help.