The term 'CELLO'S KIN' refers to three string instruments related to the cello. The first is the BASS, which is a four-letter word. It is the largest and lowest-pitched member of the string family and is usually played with a bow. The second is the VIOLA, which is a five-letter word. It is slightly larger than the violin and has a lower and deeper sound. The third is the VIOL, which is also a four-letter word. It is the smallest and highest-pitched member of the string family and is usually played with a bow. All three instruments are related to the cello and are commonly used in classical music.