What is the story of Penelope's parents' relationship?

Penelope explains her parents' relationship in that Lawrence lost his first wife during World War I and Sophie lost her parents, who were close friends with Lawrence. After the war is over, Sophie finds Lawrence because she was always told that he would take care of her. In fact, he does and they fall in love, despite their age difference. Their marriage is the ideal union and shortly thereafter they have Penelope.