Aluin was known as the Eäla of time. He had sent his three sons - Danuin, Ranuin, and Fanuin to aid the Valar in creating the physical time within Arda. Aluin himself stayed with Eru in the outer Ea. He was considered the eldest Ainu of all.
Initially Aluin was to be a great Ainu of Time and the eldest Ainu of all. He had his three sons make cords and devices for Manwë to help control the Sun and the Moon. Given that they played no part in the Silmarilion, a GameMaster could use their names to fill in critical spots of Middle-earth and beyond.The Three Ainur of Time could be reinterpreted as servants of Vaire the Weaver of Time or they could be the three direct servants to Aluin who stayed inside the Timeless Halls. Given that the Aniu were all created at the same time from Eru's thought, Aluin may instead be considered something else instead of the eldest Ainu of all.