Well, I have certainly seen the opposite. I have seen a number of cases where a parent has chosen to leave a significantly bigger portion of their estate to a disabled child because that child would need it.
Ethics is not an area in which there are right and wrong answers -- just ethical principles that do or don't appeal to you. For me, I think parents should have the right to decide how their wealth should be distributed without any "must be even for all children" constraints. But I would never choose to leave my least able-bodied child less for that reason.
I have two arguments to defend jury nullification. First of all, in our system "jury nullification" is NOT a policy. It is the name for the inevitable fact to that members of a jury can decide to vote "innocent" without being subject to some kind of interrogation.
My second argument is this: I think jury nullification is actually a good policy, because the only thing it produces are delays unless fully 12 out of 12 randomly selected citizens think this application of the law is completely unfair. If the citizenry believes a law is unfair with that much unanimity it probably IS unfair.