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

Answer 1

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.

Answer 2

family

Answer 3

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