Yeah, I get it. I believe that much of the speculation that is being put forward is based upon frustration that the story has not been added to in a long time. That is likely to change right before the show resumes, if the rumblings I heard about are true. (That would be a coup for GRRM to get the next book out before the show supersedes it.) I don't subscribe to creating a backstory of my own, and am perfectly happy waiting for GRRM to fill in the blanks. To create a scenario such as a whole myth about what Ned did to be conniving and contrary to the nature that we witness will only lead to disappointment in the end. Yes, it could have happened that way, but it is not likely and has no evidence to support it, in spite of those who rally to it believe.
It is rude, even for the king, to ask the source of a natural child. Not risky at all to avoid the subject.
What we witness is a sideways conversation about Jon's mum, from Robert. Robert has never seen Wylla, is an important tidbit of information from that dialog. And, the riskiness is not all that great, when there are likely hundreds, if not thousands of Wyllas that can be the subject.
UL, your are making a supposition that runs counter to what we know about Ned. Ned has not named the mother to anyone, in story. We see from the dialog with Robert that Robert will make his own conclusions, and really it is not a focus for him, since he thinks of his own conquests. It would be simple to see Robert machine-gunning questions, and Ned picking the ones he wants to answer in any previous or future discussions about Jon's mother. However, it is very dangerous to outright lie, since the lie might be uncovered. Allowing Robert to make his own faulty conclusions is the safest course.
It is really just as likely that entries for Jaime were not made after he disgraced himself by breaking his vow, killing Aerys. Barristan, who was responsible for the White Book, may have considered Jaime to be not of the Kingsguard after the war, when he was making his greatest accomplishments in the tourneys.
Ned does not specify that it is one or the other, and clearly she can be 18, when Ned suggests that Robert was younger when he did the deed. Ned never seems to know precisely Robert's age, on my recollection. And, generally, I would say that Ned is reminiscing about the young friend of his getting in trouble (or what should have been trouble) at what was a younger age. Clearly, if Mya is 19 in 300 AC, she was born in 281 AC. But, for some reason there is a denial here.
ETA: I have done what Ned may have done, trying to recall a younger one's age . . . 17, no 18 . . . 17 or 18, yeah 18. Rhaenys' age, 2 or 3.
Let's look at it in detail, because obviously GRRM has, when we look carefully at the statements about Robert's and Stannis' ages.
Younger than 17 or 18, granted. When is Robert Younger than 18, since that is the outside. If Robert's nameday is 12/30/262 then he is younger than 18 on 12/29/280, which would place Mya's birth at 9/29/281. That is the latest date for her birth. I still don't see why it is "simply not possible".
Yandel has lied about other publicly known events.
Mya can also be born in 281. It is likely that Mya was born in 280 or 281 if you read this part of Robert's age:
264 minus one is 263, so Robert is born very late in 262.
Late in 262 has been confirmed, if we go back to Robert's and Stannis' namedays calculations.
Mya was conceived in very late 279, through very late 280 (Robert less than 17 to 18), where her birth is between the ninth month of 280 and the ninth month of 281. Again, this leaves very little room for "long betrothal" and Lyanna objecting AT Winterfell while Ned recalls holding Mya when the betrothal is announced. We do know that Catelyn's betrothal announcement leads to Littlefinger's challenge, which is about a year after Harrenhal, even though arrangements had been made earlier. (I am beginning to think that perhaps Hoster and Rickard had a discussion about things being still "on" for the wedding before making the announcement, formally.)
I am not sure where this sentiment comes from:
at the end of the Mya Stone entry. Is there something, besides the objection that I am raising about the betrothal that prevents her from being born in 281?
Again, let me point out that Lyanna is 14 at Harrenhal, and that prior to Harrenhal is several years of winter. During winter northerners leave their abodes to "go hunting", or not at all. Rickard, and maybe Brandon would be trusted enough to escort Lyanna, but to the Vale during winter, I doubt. Mya was born during that winter, it is known. The dialog was at Winterfell, and referenced Mya as well as Robert's philandering. This all leads to Harrenhal as the source for Lyanna's observations. What was Robert doing that first night? Oh yeah, he was in a war of cups with Lonmouth. Fine thing to be doing when meeting up with your betrothed for the first time in years. Nope, I fall back to the betrothal is after Harrenhal, in spite of the World Book. (Yandel's veracity has another crack in it.)
Since the timeline seems to be yours, let me address something that still bothers me about the timeline. It seems that Mya is supposed to be born, and Robert's activities are known, when Lyanna (on the night that her betrothal is announced) talks with Ned at Winterfell.
That night at Winterfell, Ned remembers holding Mya when talking with Lyanna. Lyanna knows not just that he has a bastard daughter, but what Robert's proclivities are. Robert has never been to Winterfell before visiting Ned to ask him to be Hand, so Robert did not meet Lyanna at Winterfell. Noble daughters, especially attractive ones, are never allowed to travel without a family protector before their marriage. And, prior to the Tourney at Harrenhal is (years) winter. The likelihood that Lyanna had travelled to the Eyrie to meet Robert is about nil. So, we get down to when could Lyanna have observed Robert's behavior, to know him so well, before the announcement of her betrothal? I maintain, and feel fairly optimistic that we will learn that Lyanna observed Robert at the tourney, and that the betrothal was at Winterfell, during the (months) of winter that followed the tourney.
Your statements, above, lend a great deal of credence to this sequence. That Lyanna observed Robert at the Tourney at Harrenhal. That Lyanna heard the rumor of Mya at Harrenhal. That Ned or Brandon carried Robert's offer of betrothal back to Rickard at Winterfell, where it was accepted and announced. That the Starks all wintered at Winterfell, following the tourney.
It seems pretty clear that Elia delivered her second child some (about) nine months after the Tourney at Harrenhal. Would Rhaegar dishonor Lyanna and his wife at Harrenhal? I believe the opposite, that he gave the crown to Lyanna in respect for what she had done, but remained faithful to his wife. Rhaegar was faithful until that day when he is told that Elia can have no more children. That is during the months of winter that followed Harrenhal, and Rhaegar may have set off to have a sit down with Aemon, at the Wall before weather became really nasty. It was probably complete happenstance that Rhaegar's and Lyanna's paths crossed near Harrenhal a year or so after the tourney.
Ned visited a brothel . . . Does it mean that he availed himself of the services? No. The problem with Ned is that he was never the boy he was, according to Robert. Ned looking favorably upon Rhaegar in comparison to Ned's best friend, Robert tells us a great deal. Since it is a fictional character, it is up to GRRM to tell us the answer to your doubts, but I give Rhaegar credit, because Ned does.
Nope, there is only one Kingsguard available to guard Lyanna. Whent and Dayne are Rhaegar's personally assigned bodyguards, and they damn sure are not going to let Rhaegar ride through rebel territory unescorted.