Yes, it is. There are many real - life cases where nannies have engaged in devious behavior. Some nannies might steal from the families they work for, or mistreat the children in their care. In the 'Devious Nanny' story, it could be based on actual events where a nanny had ulterior motives, like trying to get access to family secrets or financial gain at the expense of the family's well - being.
Once there was a devious kid named Tom. He found a hidden path in the woods near his home. One day, he led his friends there, claiming it was a shortcut to a magical place. But in fact, he just wanted to play a trick on them. They got lost for a while, but finally found their way back. Tom just laughed at their confusion.
To be honest, Devious Maids doesn't have a basis in any specific novela. It was developed independently for the small screen with its own unique storyline and characters.
It's hard to give an exact number. Different publishers and authors might have their own takes on what constitutes a truly devious novel, so it's quite variable.