Geraint Wyn Cooper was the father of Gwen Cooper, the husband of Mary Cooper and the maternal grandfather of Anwen Williams. He suffered two heart attacks in 2011, and was saved from dying from them by Miracle Day. However, he fell into a coma following a third and died when the Miracle was negated.
Gwen considered Geraint the kindest man she knew. According to Gwen, Geraint was fired from his job when she was a little girl because he was believed to have stolen money from his company; he didn't. Geraint saw the problem not as being about the money, but about people not seeing him as an honest man. (TV: The Blood Line)
At the time of his daughter's wedding to Rhys Williams, Geraint and his wife were living in Swansea. On the day of Gwen's wedding, he was shocked to find out that she was pregnant, apparently with Rhys' baby. At the wedding, Gwen told him about her job. He was taken aback at the thought of aliens and of life on other planets. After the Nostrovite appeared, was chased and shot by Torchwood and the body of Mervyn was discovered dead in one of the rooms, he could not phone the police, Ianto having jammed the lines. He witnessed the marriage of his daughter and after the wedding, was given Retcon to forget about the Nostrovite and Torchwood. (TV: Something Borrowed)
At some point prior to Miracle Day, Gwen told Geraint of the true nature of the Torchwood Institute and her job. Geraint came close to death, after having a heart attack, on Miracle Day but survived. (TV: The New World)
Gwen returned to Wales to rescue her father, and managed to infiltrate the overflow camp with Rhys' help. While Gwen and Rhys were bringing Geraint to Rhys's truck, he had another heart attack and was moved to category 1. (TV: The Categories of Life) Fortunately, Gwen and Rhys were eventually able to break Geraint out of the camp before he could be taken to a module and burned alive. (TV: The Middle Men)
Geraint's family members were held hostage before being released by a team of police, but he remained safe, if in a destabilising condition. (TV: Immortal Sins, End of the Road) He was hidden after being rescued, but was later discovered and brought to the modules. (TV: The Gathering) When the Miracle was negated, Geraint regained consciousness briefly before he finally died, with Rhys at his bedside, who lay his phone next to him so that Mary could bid her husband one final goodbye. (TV: The Blood Line)