There are many possibilities involving stem cell research. Animals have already been successfully cloned and I would not be surprised to discover that a human being had been already cloned as well. The problem is that there are numerous legal issues involved with this.
There are also numerous ethical issues involved with cloning. Many will argue that it is unethical to clone a human being and that only God has the authority to create life. Others would argue that cloning will give us the opportunity to cure life threatening diseases such as cancer.
Cloning a human being is certainly possible but there is no definitive answer to whether one has actually been cloned yet.
Is it possible? Surely. Scientists have already successfully cloned animals, though I suppose it depends on your definition of "success". Humans are animals too, and a collection of tissues and organs, so certainly the scientific potential is there.
It is controversial and illegal for a number of reasons, moral in terms of our definition of humanity and life. Unethical in that most people would agree that humans are not meant to be the basis of experimentation, or at least not have that be the purpose of their existence. All humans have rights, so would clones? It is so legally problematic it boggles the mind.
So while I hope it does not happen, scientific history suggests that it will at some point.
Theoretically it is possible to clone a complete human being, but the technique has not been perfected as yet. The possibility of cloning is real enough to induces many countries like USA and UK as well as United Nations to introduce regulations for preventing or controlling human cloning.
The major stumbling block in the way of complete human cloning are the ethical issues rather than technological hindrances. These ethical considerations, in addition to imposing blanket ban on human cloning, have also restricted the resource availability for research in the area of human cloning.
This is questionable because if there is any evidence of this being a real possibility at this time, the research would be considered illegal in most countries. I read about two years ago that a Swedish doctor working out of a South American country had been arrested because he had tried and several fetus' were born deformed. However, I am honestly not sure where science will lead us.
Once upon a time the idea of bionic limbs was just science fiction let alone heart transplants and blood transfusions. I only know that science is advancing faster than our legal system can keep up with the challenges.