Robert Arryn is a cockuld

[Grunwave]

It struck me odd the likeness that frail Robert owed to Littlefinger (in the series on HBO).  I begin to think that LF and Rob Arryn bear some likeness in "seed" as well.

What if Ned concluded a falsehood: Jon Arryn had died for his knowledge of Robert Baratheon's bastards.  What if, Jon Arryn had in fact discovered that Robert Arryn was Littlefinger's bastard.

In AGOT, Both Hands read The Lineages and Histories of the Great Houses of the Seven Kingdoms.  Maybe Ned was blinded by his recent lion affliction.  Maybe Jon Arryn choose to ignore the Lannister heirs, and instead had been deposed because of certain knowledge regarding LF's son.  Mayhaps he was researching the Mocking genetics of Littlefinger.

Maybe Jon Arryn was killed because of Little Finger's cockulding.   At this point we know that the Bran incident was 2nd place to Jon Arryn's death.

[Michael Snyder]

Jon Arynn was Lord of the Vale. Petyr "Littlefinger" Baelish was born into a family in the Fingers of the Vale. Jon Arynn would not have to consult any reference to know the lineages and heritage of the small Houses owing fealty to his own House. I am pretty sure Jon Arynn could have referenced any number of documents in the Aerie and sent agents through the Vale to determine the parentage of his son.

No, Jon Arynn was studying the records of the Great Houses (of which there would have been no record of one Petyr Baelish and his family, "Great" being the operative word) for the parentage of his son. He was studying the parentage of Robert's sons and that's what got him killed, with Littlefinger acting as an agent of the Lannisters, the Lannisters not knowing he would exploit Jon Arynn's death for his own agenda.

[Rufus Snow]

Small point, but it's Jon who would have been the cuckold, not Robert (well, I believe LF had cuckolded him, but whether Robert was Jon or LF's son, I haven't yet decided....)

It's possible that Jon came to the conclusion that Robert wasn't his own during his Lannister investigation, but I do think his main thrust was about the royal succession, and I can't help wondering whether this lies behind the different tales that are told about the plans to foster Robert.

Quote

A Game of Thrones - Eddard I

"We both did." Ned paused a moment. "Catelyn fears for her sister. How does Lysa bear her grief?"

Robert's mouth gave a bitter twist. "Not well, in truth," he admitted. "I think losing Jon has driven the woman mad, Ned. She has taken the boy back to the Eyrie. Against my wishes. I had hoped to foster him with Tywin Lannister at Casterly Rock. Jon had no brothers, no other sons. Was I supposed to leave him to be raised by women?"

Quote

A Game of Thrones - Catelyn IX

"I was speaking of your sister. I proposed that Lord and Lady Arryn foster two of my grandsons at court, and offered to take their own son to ward here at the Twins. Are my grandsons unworthy to be seen at the king's court? They are sweet boys, quiet and mannerly. Walder is Merrett's son, named after me, and the other one … heh, I don't recall … he might have been another Walder, they're always naming them Walder so I'll favor them, but his father … which one was his father now?" His face wrinkled up. "Well, whoever he was, Lord Arryn wouldn't have him, or the other one, and I blame your lady sister for that. She frosted up as if I'd suggested selling her boy to a mummer's show or making a eunuch out of him, and when Lord Arryn said the child was going to Dragonstone to foster with Stannis Baratheon, she stormed off without a word of regrets and all the Hand could give me was apologies. What good are apologies? I ask you."

Catelyn frowned, disquieted. "I had understood that Lysa's boy was to be fostered with Lord Tywin at Casterly Rock."

"No, it was Lord Stannis," Walder Frey said irritably. "Do you think I can't tell Lord Stannis from Lord Tywin? They're both bungholes who think they're too noble to shit, but never mind about that, I know the difference. Or do you think I'm so old I can't remember? I'm ninety and I remember very well. I remember what to do with a woman too. That wife of mine will give me a son before this time next year, I'll wager. Or a daughter, that can't be helped. Boy or girl, it will be red, wrinkled, and squalling, and like as not she'll want to name it Walder or Walda."

Catelyn was not concerned with what Lady Frey might choose to name her child. "Jon Arryn was going to foster his son with Lord Stannis, you are quite certain of that?"

So, was there any particular reason King Robert would choose Tywin over Stannis? Did he know of Jon's own plans for fostering little Robert?

[Bael's Bastard]

Lysa makes explicitly clear that Robert Arryn is not Littlerfinger's in her rant at the end of ASOS:

""NO!" Lysa gave Sansa's head another wrench. Snow eddied around them, making their skirts snap noisily. "You can't want her. You can't. She's a stupid empty-headed little girl. She doesn't love you the way I have. I've always loved you. I've proved it, haven't I?" Tears ran down her aunt's puffy red face. "I gave you my maiden's gift. I would have given you a son too, but they murdered him with moon tea, with tansy and mint and wormwood, a spoon of honey and a drop of pennyroyal. It wasn't me, I never knew, I only drank what Father gave me . . .""