@minusninelives @rrrrrats ask and you shall receive (also i just needed an excuse to edit this, which was so much fun, so thank you for giving me these prompts)
For a moment, imagine yourself in Mithrun's brother shoes.
Your brother - stronger, prettier, more charismatic, but also distrustful and disdainful of everyone especially you - is to be sent to the Canaries. It is the rule, it is the duty of all noble houses. But you know what goes on there, Mithrun knows what happens there. Yet you see him off, bidding a temporary farewell as you do, because someone from the House has to go and it won't be definitely you. Mithrun knows this, you know this. And you wonder, very briefly, if Mithrun hates you now more than he does already.
Your brother - powerful, agile, a good soldier just as he is as an heir, if he could only be an heir - suddenly disappears. The unit he belonged to suddenly disappeared. And you're speechless because - how? why? No one wants to answer you; they will instead try to bring back a body, they promise to you. But that is not what you want. You grieve for your brother. but your own family doesn't grieve with you. Wasn't Mithrun family too?
Then you found out: MIthrun is alive.
Your brother - now weak, despondent, his eyes always looking for something that is not here nor there - is to be sent home where people can take care of him. It is not your first choice, you want him home. But he is - sick. Not quite there. He needs someone who can look after him and you look at yourself - your gait, your constitution - and you know it can't be you. So, you follow the advice of your family and pour out all your resources to find him the best of healers and caretakers. You ask yourself, almost daily, if Mithrun would ever return to who he once was.
Your brother - strong, pretty, uninterested of anything and anyone else aside from what he calls 'the demon' - is now better. He can walk on his own now, eats without throwing up on himself. The color on his skin is back and the scars of his injuries have faded into thick bumps and discolored skin. But he still isn't quite there; still needs help and probably will for the rest of his life. And you can live with that. You can provide that. Just as long as he comes home.
But doesn't. Your brother - now a husk of his former self, and you hate thinking of him that way, but you can't help yourself, the Mithrun you knew is gone - runs straight back to the Canaries. His mission is not over, he says. He doesn't care how long it takes, he says. And you see him off, again, because someone from the House has to go and it still can't be you. Mithrun knows this, you know this, and you can't help but wish, very briefly, if things would've been different if you went instead of him.
"Both Oakes and Grainger have always done well when given the right material, and each has some terrifically frightening silent moments: an uncontrollable clenching of fists from Juan as he is exiled to Spain, a subtle grin from Lucrezia as she hears her brother's groans of pleasure shift to agony." — The A.V club