Probably the only (?) Siegure shipper in existence

If I'm right, Shigure is the only second gen unit to not appear on the map in his paralogue at all. (Mitama may optionally not appear if you don't visit the village three times.)

I'm pretty sure that, since Xander joins the army pretty late in the game, his son Siegbert is guaranteed to have a higher starting lance rank than his father (Xander's D-rank vs Siegbert's C-rank).

One day, I got curious on what exactly Siegbert is learning/has learned all day as part of his duties as the future king, so I took a look at the support list scripts + his paralogue script and divided it into some catagories:

Explicitly mentioned by Siegbert himself:

- diplomacy

- politesse

- etiquette

- the art of conversation

- elocution (learned a new word today!)

- swordsmanship

- penmanship

- how to use dragon veins

- "various arts", which include the art of painting

- physical fitness, apparently (excercises?)

- military/battle tactics (land and sea!)

- also combat in general

- equestrian training (well... he does ride a horse...)

- math

- and geometry (he loves that shit)

- administration (of his kingdom?)

- history

- law

- smithing, apparently (mentioned when you craft his own weapon at the smithy)

Can be safely assumed without reading into any other supports:

- lance...manship? Is that a real word...? Anyway, I mean fighting with lances.

Can be inferred through supports of the other Nohrian royals (because if they had to learn that, it's safe to assume Siegbert had to, too)

- hand-to-hand combat

- magic (until he switched his focus to swordsmanship, like his father)

This section is merely speculation:

- possibly how to ride a wyvern? (he can always reclass into the Wyvern Rider class line)

- maybe some sort of musical instrument(s)? (Elise can play the violin...)

Shigure's A-support with Selkie implies that he used to buzz houses (in his deeprealm?)

Camilla's favorite food is steak (grilled lightly)!

Siegbert is banned from the Order's library and is possibly the only character in FEH explicitly stated to be barred entry. What the actual fuck did Siegbert do to get himself banned from the library???????

Shigure does not only sing Lost in Thoughts All Alone! In his support with Ophelia, he sings three other songs.

The following characters are stated to be younger than Shigure if they're siblings: F!Kana, Sophie, Kiragi, Mitama, Velouria, Percy and Nina.

Kiragi is the only second gen unit to mention his mother in Heirs of Fate (aside from Shigure and M!Kana, but that's because Azura and F!Corrin are their fixed mothers, respectively. They don't mention their fathers in turn.). To be specific, he mentions her in his death quote in the final map.

(Okay, this one is more of a speculation, but) Siegbert's base magic growth (without factoring in whoever his mother is) is 5% (just like Xander, by the way), despite having no practical use for it. This may be because all Nohrian royals (or atleast Xander, Camilla, Leo and Elise) had to practise magic alongside various other things. This was stated in Xander and Leo's B-support, by the way. Therefore, if Xander, the crown prince of Nohr, had to learn it, it's safe to assume that Siegbert, the next crown prince, had to learn magic, too, but showed little to no talent for it and/or took up the sword because he admired his father. Or it's because one of his reclass options that he'll always have is Malig Knight, which can use tomes and he needed some sort of magic growth, however minuscule it is. The former interpretion is more fun in my opinion.

All the second gen characters have a seperate support with a male and a female Corrin. Except for Siegbert. The scripts for his supports with M!Corrin and F!Corrin are the same. (Same goes for Rhajat, but her support with female Corrin was different in the japanese version, so I'm not sure if that really counts.) This effectively means he has one support less than every other second gen character. (This fact genuinely upsets me a bit. :c) [UPDATE regarding this: according to @corruka, there apparently was a seperate convo for Siegbert, but it seems to also have been omitted. What a fucking bummer.]

Siegbert's and Shigure's base growth rates (without factoring in the non-fixed parent they may have or the class they're in) are surprisingly similiar! They have the same growth rates in strength (45%), magic (5%) skill (45%) and defense (35%). Meanwhile, Siegbert has a better speed growth (45% when compared to Shigure's speed growth of 35% his speed is stored in his pegasus), luck growth (45% to Shigure's 25%) and HP growth (40% to Shigure's 35%), while Shigure's resistance growth is better (25% to Siegbert's 20%). Of course, all of this is moot once the non-fixed parent and the class they're in are considered.

The Conquest units actually seem to have quotes in the endgame of Birthright! Of course, they are unused, since they're not usuable in Birthright and Revelation lacks endgame quotes in general. The same goes for the Birthright units and the endgame of Conquest. Since Revelation lacks endgame quotes, this makes Fuga the only character to not have any used endgame quotes. He does have them, though. But since he's the sole Revelation-only unit...

Shiro and Nina's S-support has them planning to attend a play about two men waiting a long time for someone else to arrive. The play supposedly is mainly about the two men's relationship. This is very likely a reference to the actual play Waiting for Godot, which is also about two men waiting for the titular Godot to arrive (he never does).

Just like Elise can play the violin, Corrin can canonically play the piano! Kaze mentions that if you invite him to the private quarters.

Silas claims to know Corrin's favorite dish in his joining chapter, but it changes depending on the route. On Birthright, it's surf and turf, on Conquest, it's vegetarian chowder and on Revelation, it's tangy coleslaw.

Asugi is canonically older than Hisame.