I think that we are researching parts of the same family. William Colwell Dungey Kirby was the son of William Colwell Dungey and Emily Edith Kirby (my 1st cousin 2x removed). After your grandfather's birth, William Colwell Dungey went to South Africa in the 1890s and fought in the Boer War and later married there and had five children. Edith Emily Kirby (she and William were never married) later married into the Gilbert family and had two children with him. I would need to look in my tree to get all the details, but if you have access to Ancestry.co.uk you can find what information I have in the Kirbys3 tree. But I can tell you that you have several cousins in the UK, South Africa and the USA!
I hope that this has been useful and I would be grateful for any information you have about your grandfather's family. As far as I know, he and Ivy Francis Pipe had two children - Reginald William Kirby and Pamela Ivy Kirby. If you have any more information that you are prepared to pass on I should be most grateful.