Robin looks the calmest and the most settled out of anyone in the camp three days after they learn the truth from their commander. Chrom does not quite notice between quelling fights and keeping morale up as they make their preparations for the battle he knows in his bones will end this chapter of history; he is absentmindedly grateful for it as they go over strategy in the war room with Sumia's periodical reports and pies filtering in through the haze of planning down to the smallest eventualities.
"Mother!" It is Morgan's voice, sharp and raised and upset. Chrom pauses before he passes the tent. What could possibly get Morgan (of all people) into an argument- much less with his mother?
"Oh, Morgan," says Robin, and he recognizes the tone. It is the cadence she unconsciously uses when she sets out to sway the minds of princes: beguiling in its logic, impossibly understanding in its softness. "My dear. You know why."
"That doesn't make it right!" There is the sound of heavy boots on hard-packed ground; Morgan's pacing fills the air with a steady thrum that can only be angry in nature.
"What is one life before the winds of eternity? If there were any other path to a happy future... gods. You know, Morgan, that I would take it. I don't want to do this-"
"-but you do," Morgan says, voice hitching, at the same time as a familiar voice lashes out- "-But you will for him, Mother!"
There is utter silence. Chrom does not breathe, realizing only now that the pacing had not been Morgan's at all.
Lucina has just called Robin mother.
"...Robin, you mean," says his tactician delicately.
"I do not," Lucina says sharply. There is the sound of ruffling cloth, and then a muted gasp. "There, you see it? I thought it prudent to conceal it, considering that you and Father do not appear to be-"
"-Lucina!" Robin pleads. Robin never pleads. She cajoles, she subtly directs, she hints- she does not reveal such weakness to the world. To anyone.
"No, Mother," Morgan lets out at last. "We can't let you stay blind any longer."
More ruffling.
"...I... Naga..."
"Well, it is her Mark," says the boy, only a hint of humor tracing into the statement.
"Morgan," Lucina reprimands her... her brother?
Oh, gods.
"...this is all so much to take in."
"You didn't account for this possibility, did you?"
"No... I hadn't. I'm beginning to think it was an error on my part."
"How could you have known?" Morgan asks. It's like the anger has seeped out of him. Chrom can almost hear him deflate.
"I should have at least suspected. You have his eyes, Morgan, his nose. You set your jaw the same way when you're concentrating. Lucina, you have my face- and my hair, if I'm not mistaken. You walk like I do. Oh, gods," the unintentional echo almost makes him want to laugh, "Morgan- Lucina- he can't know."
The cornucopia of hurt, confusion, and anger that springs up at that surprises him in its intensity. He puts a hand to his mouth, pretending that the sharp prick in the corners of his eyes are just from having looked up into the sun.
Never mind that it's the dead of night. The sun has been beating down on them the past few days.
Really.
"He and Sumia- they're happily married, with a little Lucina all their own," Robin continues quietly, when there is expectant silence. "...And there's always been talk, about he and I. I know Sumia has always worried despite herself. Especially because I have nobody."
When there is continued silence, she sighs a little and speaks in a voice that is terribly, terribly tired. "Lucina, Morgan, say you discover one day- forgetting about the time travel- that your commander has two children running around that look an awful lot like his or her best friend... except the commander isn't married to their best friend, but instead, another man or woman. What is that going to look like to you?"
"...You're not wrong." Morgan is the one to concede grudgingly. "But that doesn't mean we've got to like it."
"I never said I liked it either," his tactician notes, and some of the hurt ebbs away. Not all of it, though. Chrom won't soon forget that her immediate thought was to keep the truth from him. "If it were only up to us, no politics to consider or a position of authority to maintain, I would want to tell him immediately- with the two of you, Lucina. Yes, I know. Don't look so surprised. I had to notice something, after all... not very befitting of a tactician to be unobservant. You oughtn't, by the way. You've made too many people care about you."
"Have you ever considered yourself in all of this?" Lucina's somber voice slices through the facade Robin is building around herself neatly, cleanly, and lethally, just like she moves in battle.
There is another long silence. "No," Robin says eventually. "Until recently, there was no need for it."
"Recently?" Morgan.
"Until I learned about Grima."
"...Which brings us back to the point, Mother: you shouldn't do it." Lucina. Her rhetoric when angry is scarily reminiscent of Robin's. How has he not noticed that before?
"Lucina, there's no other choice. Not truly. Not if we want to end this cycle of pain and suffering. Can't you see it? Can't anyone? One life for a universe. One life for the world's future. One life and humanity lives on. One life..." her voice grows so soft, so choked he has to strain to hear it, "...and he will not die, and neither of you will suffer, and all of our friends will have the opportunity to live to a ripe old age."
"I will suffer if you die!" their daughter bursts out, fire and fury and Chrom in a temper, and collapses into tears. It sets Morgan off, and soon enough Robin has two bitterly weeping teens bundled in her arms.
He draws a breath in and dares to sneak a peek. Robin's gaze is waiting for him. He freezes. Although glimmering with tears, still her eyes are steelier than he's ever seen them. Go, she mouths. Go now. We're not talking about this.
She turns her attention to her children (and oh, he can see that they are hers) and does not acknowledge him again, though he remains for a moment longer.
What else can he do but go?