Objectively, there isn't any. The fact that you incarnated in a way in which you inherited that karma shows that this is something you were compatible with and thus couldn't avoid. You must work to resolve this if you want to avoid this situation from happening in future lives.
A pig can't give birth to a stallion, and a horse will never have the karma of a pig, however "unfair" that may seem to either side. Humans are sophisticated beings and hence have large degrees of differentiation and rank.