They’re free to identify however they like.

Because it’s a parody of humans

Neither mom nor dad or brother makes sense here. The whole cartoon is a fail really.

Well, just stop visiting the comics community then.

Anthropomorphic objects and animals and talking cats and dogs are pretty common.
There’s a another comic posted right now of talking cats. I don’t see you commenting
in that comic about how unrealistic it is or how it is a fail by the comic’s artist.

You’re being overly-critical for no reason.

Horizontal genetransfer can be kind of seen as a precursor to recombination through gametes. mom and dad are not the worst description of the parent generation if there was some sharing of “material” before splitting…