It is reasonably common for people who are not named in a Will to inherit. The use of categories in a Will such as children, grandchildren or cousins is common because it makes sure that the family line can continue to grow, and the Will always remains in step with the growth. Similarly, the phrase issue or remoter issue is used to describe children that have yet to be born. True it is a little less personal than being named but much better to still receive than miss out while a change of Will is made.