These are the three 'things' that I've found people to believe the Nephilim to be.
Son's of God: The first batch of angels who worked with Father God in Heaven, even before humanity started. Some of the angels saw the human men and women, and went to them. They mated with them and had children of their own.
Offspring of the Fallen angels: After some of God's heavenly host mated with the beautiful daughters of mankind, they were cast out of heaven. Where else would they go but Earth, back to their families. The offspring of these 'fallen angels' were called the Nephilim.
The Son's of Seth: This was a tricky one for me to understand. They were supposedly the grandson's of Adam (The first man according to the Christian Bible) and the son's of Cain. These son's supposedly married the 'wicked' daughter's of men; the children that came from this union were the Nephilim.
So which of the three do I believe? The first one. The Son's of God.
Yes, it seems crazy, there being more then one 'Son of God' (Jesus being the first). So let me make one thing straight, well...two actually.
The term 'Son of God' can really imply any being created by God. Thus, Son of God. In Christian belief, Jesus was the only Son that god had, which is wrong. But in a different perspective, there are more then 201.
Now how do we know that there are 200 angels that fell from heaven? Well, in the book of Enoch, it says that 200 fell from heaven, and it even names a few of them.
The second thing, is that not all of the angels were male in nature. It doesn't matter what the Christian Religion says, there has been hundreds of records in many other religions that state both genders.
But, the truth that I believe, is that angels have no true gender. They are not like humans, and the don't have a true gender. Instead, they come in the form that appears best to the person they are coming to see.
In the Nephilim's case, they were cast out of heaven when they fell in love and had children with humans. They were the Nephilim, both the Fallen Angels and their children.
The children were not normal humans. They were a completely new race, mixed with human and non human DNA. This made them different then humans. They were said to be much taller, stronger and more powerful then the men of old.
This sounds crazy, but trust men, really tall, strong and powerful people are not the most 'crazy' thing we are going to be looking at.
All of the Greek legends of Zeus, Hercules, and all their powerful legends we real in a sense. All legends are rooted in truth. But like all stories, they are greatly embellished. But if you dig deep enough, you can find some truth.
Goliath in the bible was also a Nephilim, along with his four brothers. They were all eight feet tall or taller.
Also, the Nephilim that lusted after the humans were angry at God, and some sought revenge against him. So, who else to join but the most well know 'Fallen Angel' of them all...satan.
Yes, he was one of the fallen, yet many people don't realize that.
Anyway, some of the Nephilim sought revenge, and began experimenting with the DNA of Earth. This is where the legends of centaurs, cedars, bird men, and the half-and-half creatures came from.
Not all Nephilim were bad though, like Hercules. He was a Nephilim, but was good. He helped people, and became quite a legend.
Alexander the Great could also have been a Nephilim too, because the Egyptians called him 'Son of Ra'. This could have been due to the fact that he was such a powerful person, and Ra was the most powerful Egyptian god.
So however you choose to think of the Nephilim, know that not all of them are good. If you are wanting to be in contact with them, be very careful. I know of a few people who communicate with angels, and it is a very powerful experience.