Perfect Humans Project: Chaison and Maison

A young woman chosen to bear the children that will give a hidden person power. The thing is, this is something she never agreed to. She tries to save her children from the person's control. With her sister's help, the children are hidden for a time. Problem is, one of the twins has a mean streak. The other twin is the polar opposite. Sweet and docile. Which twin is which? Who is playing chess with the lives of others? This person is the king of the board, and he/she doesn't care who has to be the pawn. Willingly or unwillingly.