Geoffrey Charles Poldark was the only child of the late Francis Poldark and the elder son of Elizabeth Warleggan. He was the heir of Trenwith, which was in the care of his mother's second husband, George Warleggan, until he came of age.
Geoffrey Charles was born in 1784 to Francis Poldark and Elizabeth Warleggan. He was the pride and joy of his parents, and his family, as an heir to Trenwith. He fell unwell in 1790 and was tended to by Demelza Poldark, who unfortunately became unwell too which led to the death of Julia Poldark. In 1792, he grieved the death of Francis.
Following his mother's marriage to George Warleggan, Geoffrey Charles was adopted by him. He was excited by the idea of Ross and Demelza being invited for dinner, and was disappointed when his mother reminded him that they do not visit anymore. George told him that the time had come for his surname to be changed to Warleggan, which Agatha Poldark was unhappy about, but she was delighted when he then said he would only change it to Geoffrey Charles Francis Poldark, which made Agatha laugh.
He went on a walk with his mother, where he told her about the bank opening he went to with George, which he found boring. He and Elizabeth referred to George as "uncle", who had just returned home with Morwenna Chynoweth, her cousin. Morwenna was employed by George to be Geoffrey Charles' governess. George hoped Morwenna would make him less dependent on Elizabeth for when he leaves for school the next year, but Elizabeth was unhappy because she did not see her son as a burden.
Wanting to see Ross, he snuck away to Nampara to spend time at his father's mine, Wheal Grace. Ross told him he was welcome any time. He says that he was glad, since mining is in his blood. He joined Ross in the mine to search for rocks, where he shared his knowledge of mining to him. He then commented to Ross that he was the last of the Trenwith Poldarks but Ross joked he forgot aunt Agatha. Ross says he thinks of them often and then sent him home to Trenwith.
At home, Geoffrey Charles meets Morwenna, who said she hoped they would become good friends. He looks unimpressed and speaks to Agatha, telling her Ross sent his love and that he missed her. Agatha says she missed him too. George asked him who gave him permission to visit Ross. Geoffrey Charles responded that he would not need permission to see his own family, which Agatha agreed was quite right. However, both George and Elizabeth looked unhappy.
While walking with Morwenna, he shared his unhappiness with how George had changed Trenwith. He remembered how villagers were once allowed to walk through Trenwith and they would speak with them, but now George has put up fences because he liked people to know what he owned. Morwenna says George was kind to her but Geoffrey Charles says he will be until he gets what he wants.
He was very keen for Morwenna to be with Drake Carne, Demelza Poldark's younger brother. He confided in Drake and even gave him a Christmas present. If George had found out he would have surely punished him, Morwenna and Drake for just talking. When he heard Geoffrey Charles and Morwenna whisper about their trip to Clowance Poldark's christening, he remarked that he couldn't wait until he could send the "brat" to boarding school.
Many years later, he was attending a school in London and was befriended by Monk Adderley who became a bad role model for him, and he was uncomfortable. He was saved by Ross who was working nearby and he took him home to Trenwith, which made George very unhappy. He would later go with George, Elizabeth and Valentine on holiday in London, and found the news that Ross may have participated in a duel exciting. He then took one look at Valentine and commented in front of George and Elizabeth, that he had never noticed how much Valentine looked like Ross. It finally made George accept that Valentine was definitely Ross's child.