Nicholas van Rijn, Adzel and David Falkayn appear in separate stories. Then the team of Falkayn, Adzel and Chee Lan works for van Rijn. However, van Rijn appears only once, briefly, explaining the new trader team idea to Falkayn. Thus, when, in Satan's World, Falkayn has been kidnapped and his team-mates have to contact van Rijn, this is the first occasion when we see these two characters conversing or interacting with their employer. Satan's World is the first of three works featuring all four characters. After that is a story about Falkayn's grandson who is also van Rijn's great-great-grandson.
That is quite a future history. Robert Heinlein's original Future History is built around successive historical periods but not around any continuing characters. Poul Anderson's Technic History is built around both. It incorporates three novels featuring van Rijn, a trilogy of novels about young Dominic Flandry and three novels featuring the older Flandry. None of these works is a future history in itself but, when added together, they are more than the sum of the parts.