Which level of biological classification do Mammalia and Hominidae represent, respectively?

The answer is class and family.

Taxonomic groups are used for biological classification. There are eight main taxonomic groups: domain, kingdom, phylum, class, order, family, genus and species, with the domain as the most inclusive and species as the least inclusive. If we take a look on Mammalia and Hominidae classification, we can assume that Mammalia represents class, and Hominidae represents family:

1. Domain: Eukarya

2. Kingdom: Animalia

3. Phylum: Chordata

4. Class: Mammalia

5. Order: Primates

6. Family: Hominidae

7. Genus: Homo

8. Species: Homo sapiens