well I'm not sure about related but they are both crustacean's . maybe lets go with yes...
Horses are vegetarians, they do not eat shrimp or crabs.
hermit crabs are not true crabs, but are more closely related to shrimps. I read it in a book!Hermit crabs are more closely related to squat lobsters and porcelain crabs than they are to true crabs.
prawns
Yes, a shrimp is a shellfish as it has a hard outer shell.