Forbidden desires (he's a brother and more!...)

Forbidden desires 
    (He's a brother and more...) 
Synopsis 
    Maxwell and Mandy were both left in the hands of their nanny by their patents. The couples are always traveling from country to another for business leaving little or no time at all for their kids. The Parents believed that the most important thing for a parent to do is to take care of the kids needs and wants, ensuring they don't lack anything. 
  Mandy and Maxwell becomes very close because they believe that all they have is each other. 
  When Mandy reaches adolescent age, her friends suggests that it is time for her to go into a relationship but Mandy disagrees with them claiming that Maxwell hasn't brought the topic up and if her brother doesn't bring the topic up, it is of no importance. This was how much Mandy trusted and relied on her big brother, Maxwell opinion. 
  They become over protective of each other but what happens when their love becomes an obsession?.
When Maxwell can't stomach the thought of  his sister, Mandy being with a guy?... 
 When they engage in the forbidden romance?... 
     When Maxwell intends on being mire than a brother?... 
 When they commit a grave, serious, delicate, sin... 
   What happens when one of them wants out in the relationship?...