Are arthopods most closely related to same family, class, genus or species?

Answer 1

Arthropods are a phylum of animal that has nearly all the invertebrate life with an exoskeleton,jointed legs.
4 extant subphylums as such:
Subphylum Chelicerata - Chelicerates
Subphylum Crustacea - Crustaceans
Subphylum Hexapoda - Hexapods
Subphylum Myriapoda - Myriapods
Each of those further divide into the class of animal
https://en.wikipedia.org/wiki/Arthropod

Answer 2

family

Answer 3

Your question is incomplete. Most closely related to what?

Are you asking at what taxonomic level are the Arthropoda (arthropods)? Then that should have been your question. The arthropods are a phylum. It is a very large phylum containing more species of animal than all other animal phyla combined.