He closely oversaw his sons' education and taught them foreign languages. They were sent to a military academy in Germany. Frank died when a young man while serving as a soldier in the Prussian army. His son Edward converted to Catholicism and told people that he was the son of Sir John Trelawny. They later became estranged. Zella became a housewife in London. Trelawny outlived four of his seven children. The only child whom he enjoyed good relations with was Laetitia, who also lived with him in Sompting. He had chosen to name her Laetitia as several women on Sir Johnathan's side of the family were named Laetitia. Late in his life he became a teetotaler and vegetarian.