Duncan comes from a small family in Dublin. His father is a Wizard originally from the same town. He had attended Hogwarts as a child and specialized in herbology. Duncan's mother is a muggle who comes from a smaller town in Ireland. She moved to Dublin as an adult to find better work than she could in the countryside. Duncan's parents met there when his Father was out gathering supplies from muggle shops for his garden. She too was hoping to start a vegetable garden at home so they met at the shop. They fell in love quickly and chemistry, or maybe magic, pushed them together from the start.
Duncan was the first of two children, his younger sister being two years behind him. His childhood was a mixture of muggle culture and wizarding world culture, but he always loved the magical world more. Their family ran a large greenhouse that supplied potion masters and supply shops in town. There would always be plants in and around the house whether muggle or magical.
Despite all the plants in the family, Duncan is not certain he wants to take the same path yet. He wants to explore all Hogwarts has to offer before choosing his own career. That said, his knowledge of Herbology is likely higher than most students in their first year at Hogwarts. He is fairly outgoing and likes to try new things but he is not the bravest kid when it comes to taking big risks.