Jeff, thought it would be fun to change her into an infant, so that's what he did. The first thing to change was her clothes. Her top disappeared and her breast hanged out in the open. Her underwear and pants slowly morphed into a bulky diaper.
Jeff was pretty aroused at the sight of his sister half nude and in a diaper but the changes continued. Her legs shortened and her height kept going down until she couldn't stand. Jeff could see the intelligence leave her eyes until she looked very dumb and infantile. Her body shrunk to that of a child. Her hair turned into pigtails and the changes ended with the glass of milk turning into a bottle that she was intensely sucking on.
His mother came around the corner and was confused on how she got out of her crib(which didnt exist until moments ago). So she laid her in her crib.
Jeff saw this and got an idea....