William Roger Dean was born on 31 August 1944 in Ashford, Kent. His mother studied dress design at Canterbury School of Art before her marriage and his father was an engineer in the British Army. He has three siblings, brother Martyn and sisters Penny and Philippa. Much of Dean's childhood was spent in Greece, Cyprus, and, from age 12 to 15, Hong Kong, so his father could carry out army duties. Dean was very keen on natural history as a child, and Chinese landscape art and feng shui became particular influences on him during his time in Hong Kong. He has cited landscape, "and the pathways through it", as his greatest influence and source of inspiration.