Here's a breakdown of their relationships:
* Whales: Whales and dolphins are all cetaceans, but whales are typically larger and have different body shapes than dolphins.
* Baleen whales: These whales have baleen plates instead of teeth, which they use to filter krill and other small organisms from the water. Examples include humpback whales, blue whales, and gray whales.
* Toothed whales: These whales have teeth and include dolphins, porpoises, and other whales like orcas.
* Porpoises: Porpoises are small, stout-bodied toothed whales that are closely related to dolphins. They have a more triangular dorsal fin and lack a beak.
* Other toothed whales: This group includes a wide variety of whales, such as orcas, pilot whales, beluga whales, and sperm whales. They all share a common ancestor with dolphins.
So, in essence, dolphins' cousins are all the other whales and porpoises, as they all belong to the same order.