Yeah, given the importance of music and poetry in Tolkien’s world, starting with the very music of creation, it is a surprise there is no god of music. Also no one for childbirth or harvest although Yavanna probably governs the latter. And who keeps the terrestrial animals? Fish and aquatic animals are Ulmo’s, birds are Manwë’s but who takes care of mammals?
I also wondered about the siblings and the fact that most of the
Valar are married or “together with” another but none have children. This is very different from, say, the Norse or Greek pantheons
Zeus and Odin have offspring all over the place, both in their godly domains and among (and born of) humans. We do however know that it is possible for at least some
ainur to procreate (more on that later). But, what makes some of them siblings? And Vána is even the
younger sister of Yavanna.
Furthermore I strongly appreciate the fact that two of them remain unmarried, there is even a goddess who doesn’t have a spouse while most others do! Unexpected but great.