Linhardt and Seteth should've gotten supports honestly. If Bernadetta thought Seteth and Cichol were similar, Linhardt would've been onto him for sure
Linhardt would absolutely sniff Seteth out.
C support, Seteth finds Linhardt in the library during class/a war meeting and calls him out for being lazy. "You bare the crest of Saint Cethlean. She was a respected healer and possessed immeasurable kindness. For you to act so selfish and uncaring is an insult to her memory."
And Linhardt, unfazed by the insults, is like, "You sound personally offended. It’s as if you knew Cethlean yourself."
Seteth: -scoffs- Do I look so old to you?
Linhardt: I feel like I shouldn't answer that. Anyway, you're right that it's because of my crest that I have an affinity for healing. But that hardly means I have to be the next Saint Cethlean. One is enough for the history books, don't you think?
Exasperated, Seteth gives up and leaves. Linhardt ponders why Seteth cares so much about Linhardt and his crest.
Their B support might start the same way. Seteth approaches Linhardt in the library-- but this time Seteth compliments him. “I heard you helped out a battalion that had been caught in a tight spot. Thanks to your efforts, we didn’t lose a single soldier.”
Linhardt tries to brush it off like “right place right time” or “never underestimate how much I detest the sight of blood” but Seteth shakes his head and says Linhardt did good work out there. Linhardt turns to him and says, “Let me be blunt, Seteth. Are you overly concerned about me because Saint Cichol, who bore your crest, was the father of Saint Cethlean? Is that where this is coming from? Because I’ll have you know I already have a father and don’t need another one.”
Seteth denies this up and down but Linhardt isn’t convinced. “Perhaps it’s our physical similarities, then. I do look as though I could be a child of yours. So does Flayn, for that matter-- though I suppose she is your sister after all. Come to think of it, do you ever lecture her on acting more like Saint Cethlean?”
Seteth: Of course not. Flayn already uses her gifts to their full potential. She is a prime example of what Saint Cethlean stood for.
Linhardt: I once again have to wonder how you came to be so sure of who does or doesn’t act like a saint.
For their A support, I don’t know that Linhardt would go so far as to accuse Seteth of being a saint but he would get a sense something was being concealed. Maybe Linhardt goes to Seteth this time. He tells Seteth that he looked through some old tomes to find out all he could about Cichol so he could accuse Seteth of not acting like him at all-- except what Linhardt found was that Seteth sounds a lot like Cichol.
Linhardt: It’s strange, really. It’s as if you modeled yourself after Saint Cichol. Unless... no, that can’t be it.
Seteth: I did not set out to mimic Saint Cichol but I consider it a compliment to be comparable to him.
Linhardt: Of course you do.
IDK how that interaction would end but Linhardt would definitely have Seteth on his radar after all these talks. Maybe Linhardt even points out at some point that a family having children with two different major crests is so unheard of that Linhardt can’t find another instance of it anywhere. “Weird, huh? Any family secrets I should know about?” to which Seteth makes a hasty exit.