Well, on the subject of the three rings I don't think it was as _dangerous_ to disclose who
the ring bearer were to a select few.
Isildur would qualify under this "select few". Considering that one of the
ring-bearers,
Gil-Galad was slain in the war (though he "gave his rings to
Elrond, when he found
Rivendell and
Círdan) and there may have been discussion on who should now have his rings and who would make the best use of them. Isildur, as the new "king" of the
Elves closest and greatest allies, the
Númenóreans. He was also a "
ring bearer" even though Elrond and Círdan were not too happy about that. He may have viewed any secret discussion or discussions which excluded him, as an aggressive move on the part of the Elves, who had already voiced their misgivings about him keeping the ring. Were they trying to ostracize him? Were they jealous of his new-fangled power? As
Tolkien states, Isildur was a man of "great vigour" and he would have wanted to get involved with any discussions or councils, him being one of the most important leaders in
Middle-Earth. Somehow I think that Isildur was a bit of a egoist. The ring may have acted as a catalyst in his egotism. The rings sure played on the weaknesses or desires of it's bearers. Isildur was also pretty bellicose and impetuous.
So, Isildur may have been informed about the ring due to necessity and to avoid trouble and because he was a ring bearer, and possibly because the Elves wanted to tell him. But of course, they should have known about the possibility of the ring enslaving Isildur's mind and the risk that came with telling the bearer of
the one about the Elves rings. Wasn't there an essence of superfluity and risk in telling Isildur about her rings? Plus, Elrond knew that
Sauron was not _dead_ or to be fastidious about it, he knew that Sauron was still a potent (though vanquished) force, brooding somewhere in
Arda until he felt it was time to come back. It could be in 500 years or a thousand or even 10 thousand. And so even if at the time Sauron was not the salient problem, he was still somewhere lurking in the background. Also, Isildur could have refuted some of Elrond and Círdan’s arguments. Why didn't they destroy _their_ Elven rings? They were a risk too weren’t' they. So he may have though that the Elven argument was a cognitive dissonance, the Elves, in telling Isildur to destroy the ring are forgetting about and contradicting their own weakness in not destroying "their" rings and their refusal to destroy the rings after the overthrow of Sauron. This may have hardened Isildur's desire to keep the ring, what was (in his eyes) a blatant case of
Elvish hypocrisy. Of course the ring would have been "messing with his head", considering that he was so close to Mount Doom. Ringbearers get a lot crazier the closer they get to Mount Doom. Or rather the perfidious Ring's powers of persuasion are greater the closer you get to Mount Doom. Remember he tells Elendur that his "pride has fallen". Did he think he could control it or something?
Isildur may have found out about the Elves rings whilst he was wearing the ring. But this is impossible. He only wore it once, after he cut it off Sauron's finger, and the Elves weren't wearing their rings at the time. So such an argument may be fallacious. He may have seen them without actually wearing the ring.
Or what if the Gil-Galad told
Elendil about it at one time or another. Did he trust him enough to tell him? Most definitely? But was it safe to tell him? Not really. Who knows. I don't think Gil-Galad was capable of such foolish actions. Even
Aragorn reprimands
Frodo for telling him that
Galadriel is a ring-bearer. And would Elendil tell Isildur? Or was it necessary for the Elves to tell Elendil or his sons about the Ringbearers?
Isildur seems to be pretty careless about the "secret". He tells his son, we can even gather, by his words to Elendur that Elendur knew something of the matter beforehand. Elendur was of course in his father's full confidence, and rightly so. Admittedly the Númenóreans were practically at deaths door anyway so even if he did spring it on him then and there it wouldn't have mattered very much. Though their conversation was obviously overheard. It was still pretty risky.
Perhaps he was informed when G-G gave his ring to Elrond before his death.
Gil-Galad gave the ring to Elrond when he set up
Imladris. Tolkien gives two different
dates for the giving of
Narya to Círdan. One states that he gave it to Círdan as soon as he received it and one that he gave it to him close to the
events of the Last Alliance. The former view is the "canonical" one.
)
