Billionaire in a Kid's Body

Greyson cut his mother out of his life because his father lied to him, and he did not find out it was a lie until he was on his deathbed. By then he was the richest man in the city, it was too late to make anything right, and he died full of resentment. He wakes up as a child on the day his parents get divorced. This time he stays with his mother and sets out to hit back at his father. He makes money in the stock market, and through the trading he meets a young man with a fortune of his own who joins him. Together they set about exposing his father's mistress, and after that they deal with a second woman who has been working against them.