Two Eyes From The Brothers Grimm Fairy Tales

One of my favorite short stories was One Eye Two Eyes Three Eyes from the Brothers Grimm fairy tales. By the title you would assume it was about witches or shrews but alas it contains none of the sort. The story starts with three sisters and a mother, one sister had one eye, one had two eyes and another three. When setting up the background for the story a line states “Thou, with thy two eyes, art no better than the common people” this was said by the mother to two eyes. Throughout the tale two eyes is treated badly and luckily a prince wanting an apple from a tree sprouted from magical goat guts took her away to live a life of wealth and leisure in a plot line that can only make sense in a fairy tail. What interests me in this is that

the sisters and mother felt superior because two eyes was average. She had no disadvantage or handicap from having two eyes that burdened her or her family, nor did she have an advantage by having two eyes for them to be jealous of. It doesn't make much sense to me where the resentment is coming from.
The tale resembles Cinderella vaguely, containing a neglected/abused child and evil sisters and mother. A difference between the stories being that the mother in this story is related to two eyes, in cinderella she was a step daughter. As horrible as the reasoning is I can understand that as cinderella was a step child how the step mother would prefer her own blood but in this story it is her blood daughter how would someone shun their own blood. I am aware that it happens in abusive homes and sometimes to only one child like in ‘the boy called it’, but it still defies reasoning.
In the long list of ways this story has unreasonable characters high up on the list is that the mother has two eyes, why would you teach your children to mock and hate someone for a trait that you have. The thing that makes the most sense is that she is resentful of the quality in herself but is directing the hatred to her daughter.
The birth order of the three girls also pokes holes into reasons why two eyes would be ostracized. When two eyes was born three eyes was not there yet, the mother would have no way of knowing that her next child would not also have two eyes and one eye would have been the odd one. We would assume that she had been taking care of two eyes at least until she became the odd one out with the birth of her three eyed little sister. When three eyes came into the picture she most likely had already bonded with two eyes , simply through the amount of time and effort she would have had to spend with an infant two eyes, it doesn't seem likely that she would shun a child she had taken care of and bonded with.
The mother may have been resentful from the start that two eyes was not special as one eye but again, when she got pregnant again she had no way of knowing the number of eyes on her unborn child. If she was born with two eyes would she have been shunned too? the reasoning of this woman is erratic and illogical. Clearly whoever gave two eyes the magical food goat saw how far from reality the mother was and did the logical thing of helping with a enchanted horned farm animal. I applaud him and his simple solution to the problem.