Lets be clear about one thing: Dragons pre-date humans in fairytailverse. They are the original species of the world and the original wielders of magic. What happens is that humans, if they bathe too much in dragon blood, AKA kill a lot of dragons through the use of dragon slaying magic or its overuse, will become able to achieve a full transformation into a dragon. They aren't, however, dragons. Acnologia is not a dragon. He is a human that has a very buffed up version of Dragon Force that goes beyond making him have scales and "dragon eyes" but actually transforms him into a dragon. So no, this new guy isn't a dragon.
If he is named Dragneel we know he is of the same family as Zeref and Natsu. Natsu, however, isn't really Zeref's brother but rather a demon he created using black arts and his brother's body. He's a...clone of sorts. And its that whole background that justifies most of Zeref's abilities and what he is today. I doubt, therefore, that this new character is a brother of Zeref. Why would the author not mention Zeref had another brother when he detailed Natsu and Zeref's relationship so well. I mean, it would be a bit of a poor plot to add another brother. It would devalue the relationship Zeref-Natsu and there fore, zeref's background as well.
It can be a son of Zeref or simply another creation of his. It could even be a surviving relative of the same family.
I don't think its an opposite to Zeref mainly because he's part of the spriggan 12 so....why would an opposite, help Zeref?
I also don't think its an Edolas version of anyone. Mainly because, from all Edolas versions, Mystogan was the strongest we saw and even he wasn't on the level we now have Laxus, Natsu, etc. Considering what we saw so far, August, Eileen and this new guy are within the springan 12 in a whole other level. So, Mystogan, with magic tools, is much weaker than any of those. Its not a stretch to say that even with magic tools, one from edolas cannot be on the same level as mages from this reality. How would a weak guy that uses a magic tool be able to be in the springan 12? Doesn't make sense. He needs to be a mage and therefore, from this reality.