It's my opinion that Willie and Robert may have instigated Tad just a little.
Isn't that what big brothers are for?
As the youngest, Tad may have gotten away with some things the others didn't.
Plus, with his speech impediment, his parents may have been a little more lenient with him.
I wonder if Herndon didn't exaggggerate some of the children's actions like he did Mary's.
So when is this "Old Enough To Know Better" supposed to kick in?