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.