* Whale sharks are not closely related to other sharks. They belong to a group called Rhincodontidae, which has only one species: the whale shark.
* "Sister" refers to a close evolutionary relationship. While all sharks share a common ancestor, the whale shark diverged from other shark lineages a very long time ago.
* The closest relatives to whale sharks are actually rays. They are part of a larger group called Elasmobranchii, which includes sharks, rays, and skates.
So, while it's fun to think of a "sister shark" for the whale shark, it's not a scientifically accurate term.