With every playthrough I grow more and more convinced that Loghain was right about Eamon being a manipulative jerk who cares little for Alistair, aside from wanting to make him into his puppet.
Teagan actually shows more joy at seeing Alistair alive and well, as well as more affection towards his "sort-of nephew" than Eamon ever does in Origins. And it's Teagan who comes after Drunk!Alistair in DA2 and convinces him to try to reclaim his birthright, (although it could have been on Eamon's orders). For the most part, Eamon seems to just wash his hands of Alistair if he doesn't become King.
Of course, since he's trying to overthrow Anora and kick her off the throne, it's possible if she becomes sole ruler she chucks him in the dungeon.
Loghain was definitely right about Eamon. Not a single thing Eamon does gives any indication that he cares one iota about Alistair beyond using him as a puppet for the throne one day. Nothing in the past and nothing in the present. Kind of why I love to just keep Alistair as a warden in most games unless I become queen and rule beside him in which case I don't care what the epilogues say, Eamon is out. Teagan would likely be given preference over Eamon since Eamon already has redcliffe and yes, Teagan is happy to see him and is the one who shows up to help him.
What always amuses me is how upset Alistair gets if you don't save both Isolde and Connor. You can use cunning or persuade to limit how badly he takes it by shoving in his face that he's more upset because it was a personal thing but it would be nice if you had another option to point out that while he thinks he owed Eamon something, Eamon did absolutely nothing for him but allow him TO THINK he did something for him. He actually put alistair in the chantry which alistair HATED and because he hated it so much he picked being a grey warden just to get out of it. So technically, Eamon is responsible for Alistiar's taint, likely not having children, and his eventual death due to the taint, and if you really want to get down to the truth of it, Alistair doesn't even like being a warden (which he admits in the fade but apparently is in denial of while awake). If Eamon hadn't packed him off to the chantry and maybe just let him be a soldier, Alistair might have had a shot at a decent life one day. He could have met a woman, married, had children - the family he always wanted... so really, all of that is Eamon's fault. I suspect the chantry was even chosen so that he could easily find alistair if he ever needed another heir.