top of my head...

I would say that if this stuff interests you, you should pursue it and see where it leads you. A good translation of the Enuma Elish is a decent place to start. Read Gilgamesh again with a critical eye, and then go back and read about Enoch, Elijah, and Ezekiel. The parallels are incredible. I would recomend you go even further and find a copy of the Book of Enoch (Apocrypha in most traditions, but cannon gospel in the Ethiopian church among others)... there are a few versions. The Book of Jashar, The Book of Jubilees, and other tomes of that ilk are also worth checking out. Often the books that were left out of the Bible were ones that spoke too much about the Nephilim and such things.

I would go ahead and keep reading Sitchin as well. Funny that you mentioned Don Juan Matus... Carlos Castaneda was another one who was the subject of intense controversy and outright pillorying. Many people believe that he made all that shit up. Obviously, what he presented wasn't a "Yaqui way of knowledge," and he got around to making that clear... but there is mad truth in what he did say. In the end, it doesn't really matter what is true. Don Juan & Don Genaro live in our imaginations. This is how I feel about the Sumerian stuff as well. Is it true? Is the Bible true? We can say that a huge number of people believe the Bible is true. We can also say that a huge number of archaic civilizations believed in Sumerian style gods and their imperfect, emotional, quarrelsome and warlike interactions with each other and with humanity. Both the Bible and Sumerian epics state things that we have verified through archeology.... Personally, I don't think that the statements of 5 people who witness a car accident taken 15 minutes after the fact can be regarded as truth... so we're back with taking responsibility for what you choose to believe. Look discerningly at all information and evidence. Follow your gut. Just be open minded enough to let the Universe change your mind.

As for "any relation?" I would have to say "Of course!" We are all related intimately and dynamically. The Native Americans have a greeting along the lines of the Hawaiian Aloha, the Hindu Namasté, or the Hebrew Shalom which is "Aho Mitaquiasin" roughly translated, this means "to all my relations...." and that means everyone.

Ciao.