The term 'whale relative' can be summarized by two crossword solutions: HIPPO (5 letters) and ORCA (4 letters). Hippos are large, semi-aquatic mammals native to sub-Saharan Africa. They are the third largest land mammal after elephants and rhinos. ORCA, also known as killer whales, are the largest member of the dolphin family and are found in all oceans around the world. They are highly intelligent and social animals.