Myths have them. Numerous gods and demi-gods. Some religion also hint at their existence. Muslims for example believe djinns are more powerful than humans which technically makes them demi-gods since they can do things which humans can't. Christians and Jews have this story about angels [gods] some of whom expelled from heaven and a second group angels who came down to earth so they could get married and they produced hybrids who were the heroes of old. Since these fallen angels never did depart and their offspring had nowhere to go [when they died] since they were children of angels, does it mean that we still have these gods and demi-gods around?
Well if you believe in that, then logic would state that a lot of us have ancestors that were demi-gods... so there would be some supernatural part in a lot of us. Then again if you believe in angels and demi-gods I'm not sure what your take is on the evolution theory, which is where this whole passing down genes comes from. But for me these have always been just myths... just interesting stories that were passed down from one generation onto the next one.
I believe that there beings that have existed grwater thsn the human form. Notnsure if they're necessarily gods or demigods.
Personally I think they are myths, nice stories that made us believe that Gods make errors too. I remember watching Percy Jackson (a children's movie on a demi-god) and it did seem far fetched then, but more for fun. Even if angels decided to come in human form, I don't think they relinquish their knowledge or power, but it doesn't pass on through hereditary genes. Wings are earned.
I personally don't believe in such thing. It's been created to manipulate humans, keep them behaving. That doesn't mean I'm not respecting society's rules, but if you really need religion, namely gods and demigods, to be kept under control... then you might have a psychical problem, really.
You could extend the meaning of demi-god to so many things and it is a question on what you believe. If the human race develops a way to become immortal then could you say that we have have become gods or are simply playing god. Someone who overcomes an illness that was guaranteed to take their life, or someone who survives an event or illness in miraculous circumstances, could you then say that they are demi-gods?
For me the answer is a clear and absolute no. Others may believe differently but I'm not interested in debating it. I believe in a singular (one and only one) God and no variations of. Anything else is myth or misunderstanding.
Law and order in society preceded religion. Pagan religions didn't have rules/commandments which had to be kept. All there was to it, was sacrifices to gods to seek their help say at a time of war or thank them for any good fortune. IMHO, all that talk that religion was created to control people isn't entirely true.
NO ONE can say for certain if there is a God, or multiple Gods or whatever. There could be, there could not be. The entire thing is way beyond what we are capable of understanding. BUT just looking at the world, and the way things work, it's pretty obvious the conventional idea we have of God(s) is incorrect.
I do not believe in demi-gods. However, if they were to exist, one would hope that they would play important, beneficial roles in the countries of the world.