Responses
Considering little rabbit MC back story, he may be a clone too, and adding the several facts like maybe he being from a different bach of experiments, meaning different conditions than MC, we can safely say he can pass as a son, biologically speaking, maybe like the ones that are incubated outside the womb kind of type. Well, no ML gene tho.

wait is that child rabbit the one from "the falling merman"? Their son? I didn't know he was adopted