Coelacanths are indeed related to other living species, albeit distantly. They belong to a group of fish called Sarcopterygii, which are also known as lobe-finned fish. This group is significant in the evolutionary history of vertebrates because it includes the ancestors of tetrapods, which are four-limbed vertebrates. Tetrapods gave rise to all land-dwelling vertebrates, including amphibians, reptiles, birds, and mammals.
So, while coelacanths are not closely related to any living species, they share a common ancestor with the lineage that eventually led to tetrapods. This deep evolutionary connection makes coelacanths important from a biological and evolutionary perspective.