Zaidy78 I am very glad that you brought to light the Gemara in Tractate Shabbos regarding four people who dies without sinning.
As you most correctly stated: “Only four people in the history of world died without doing any aveiros whatsoever. The only reason they died was because of the g’zeira from Adom and Chava. One of them is Amram.”
Zaidy where I respectfully disagree with you in regarding your comment concerning Amram marrying his aunt: “How could Amram have married his own aunt? If you will say that it was before matan Torah, so then the whole gemara looses its punch. ” I do not think the Gemara loses it punch at all. Meaning that a person is required to observe Halochos that are in existence and in force in their lifetime. I believe that the challenges facing the children of Israel in Egypt to keep the Bnei Noach laws were no less difficult than the challenges that we have today to keep all the Mitzvos as Torah Jews. As it was stated by other respondents in this discussion, Idol worship as well as actions forbidden to Bnei Noach was rampant in Egypt. Thus, it appears to me, that Amran is listed in the Gemara as one of the four people who died without sinning on their own because he, in fact, kept all the laws that he was required to keep- i.e. the Laws of Beni Noach, a task at the time, that was much more difficult than meets the eye. Therefore, we do not need to ‘explain away’ through calculations the reason why Amram married his Aunt. It was completely permissible for a Beni Noach to do that and the Gemara inn Tractate Shabbos stating the he died without sin clearly validates this.