You can just look this stuff up on wikipedia...
https://en.wikipedia.org/wiki/Family_(biology) "Family (Latin: familia, plural familiae) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between order and genus."
https://en.wikipedia.org/wiki/Equidae "Equidae (sometimes known as the horse family) is the taxonomic family of horses and related animals, including the extant horses, donkeys, and zebras, and many other species known only from fossils."
https://en.wikipedia.org/wiki/Bovidae "The Bovidae comprise the biological family of cloven-hoofed, ruminant mammals that includes cattle, bison, buffalo, antelopes, and goat-antelopes. A member of this family is called a bovid."
No, horses and cattle are not in the same family. Nor are they in the same clade; cattle are artiofabula, (ruminants) horses are mesaxonia. (odd toed ungulates) https://en.wikipedia.org/wiki/Artiofabula https://en.wikipedia.org/wiki/Mesaxonia
> But to also be fair, if you want to classify horses and cows as edible based on their shared common ancestry, you’re also arguing for eating giraffes, tapirs, rhinos, hippos, whales and dolphins.
The argument is about whether horses and cattle are in the same family, not that a species' taxonomic classification can be an indication that they ought to be eaten.