He decided he was going to cast a spell on Zarah. Then she could help out around the place more if she was older.
He grabbed the book. Then he found the spell he wanted. He went to where Zarah was playing. Then, he quietly read the spell.
He watched his younger sister. She started to get taller and older. Soon she was the same age as Kel.
She had a few changes. Her hair now went to the bottom of her shoulder blades. Her face matured quite a bit. Then her chest changed. It pushed out to A-cup boobs. It was bigger than what she had before. Her hips pushed out a bit too. Lastly, her clothes matured.
Then...