All that is gold does not glitter

[Megorova]

1 hour ago, Jaehaerys Tyrell said:

Although I’m astounded than Jon Arryn didn’t have any suspicions about the pair given than Lysa was clearly persuading him to promote Petyr. 

Maybe he didn't cared. She was his third wife. She was not an heir to Riverrun. They married not out of love, it was arranged marriage, to create a war union between The Vale and Riverlands. He was old enough to be her grandfather. Maybe he was unable to "perform". But he needed a heir, because his son got killed in the beginning of Rebellion. So maybe he and Lysa agreed, that Petyr will be their "surrogate" father. Like in the Bible - Abraham, his too old wife Sarah, and surrogate mother Hagar, that was Sarah's handmaid, and gave birth to Abraham's son. Hagan was servant of too old Sarah, and Petyr was a bannerman of too old Jon.

[Jaehaerys Tyrell]

6 hours ago, Megorova said:

Maybe he didn't cared. She was his third wife. She was not an heir to Riverrun. They married not out of love, it was arranged marriage, to create a war union between The Vale and Riverlands. He was old enough to be her grandfather. Maybe he was unable to "perform". But he needed a heir, because his son got killed in the beginning of Rebellion. So maybe he and Lysa agreed, that Petyr will be their "surrogate" father. Like in the Bible - Abraham, his too old wife Sarah, and surrogate mother Hagar, that was Sarah's handmaid, and gave birth to Abraham's son. Hagan was servant of too old Sarah, and Petyr was a bannerman of too old Jon.

I considered this but it just doesn’t seem fitting with Jon’s character. He’s said to be proud like many Arryns, and it would be a huge decision to have the ancient Arryn line pass to a bastard that I just don’t think he’d take. There is Harry the Heir and many Arryn cousins. Even if he was the last Arryn I’m sure he’d rather the Eyrie go to something like House Royce rather than a Baelish bastard.