But Rhaegar died before Lyanna did, and never got to meet Jon.
I see why Lyanna had to die in labor. Easier for GRRM to write and set up his story .
...and why does everyone assume that she died in child birth? here's the more likely story:
R&L were in love and were secretly together, maybe even wed, even though he already had a wife and she was engaged. Remember, it wasn't unprecedented for Targs to have more than one spouse. They had their love nest in Dorne. This would also explain why there were members of the Kingsgaurd protecting her.
My theory is that Aegon had already been born. If they were secretly wed, that would be important because otherwise Aegon would have been a bastard rather than a prince.
Unfortunately, Robert was still in love with Lyanna and wasn't going to let a little thing like her being in love with another stop him from claiming his bride. He claimed that she had been abducted, which was better than suffering the insult of having been jilted, and went to war to win her back. Since Lyanna had disappeared with Rhaegar, Ned believed Robert's account of how things went down.
So, Rhaegar leaves Lyanna and their new son to face Robert and dies in the battle of the Trident. When he dies, it rains red rubies (fire) from his shattered breastplate.
Ned races to Dorne thinking that he is rescuing Lyanna. News has reached her that Rhaegar is dead, and she believes that they have come to force her to marry Robert. She knows that her son, who is an heir to the throne, is also in grave danger if Robert finds out about him. Grief stricken, she takes her own life (stabs self, cuts wrists or the like). Ned finds her dying and she tells him the truth and makes him swear to protect her son Aegon. As she dies, she drops the blue rose petals that she had been clutching (ice).
Afterward, Eddard takes Aegon to Winterfell. He can't very well say who he really is, and calling him Aegon would be kind of a giveaway, so he claims that he is his own bastard and calls him Jon Snow.
This post was edited on 6/24 at 9:31 pm