Cavaliers tend to be around the same age/older then their necromancers.
We all know Gideon is 18 and internally she is the most 18 year old to ever be 18. Shes also super muscly and wearing skull paint that probably hides the leftover baby fat and pimples.
What if everyone at Canaan house just assumed that Gideon was a good 5-10 years older than Harrow like the 2nd/7th/8th houses. What if they thought that Gideon was being quiet so to not disagree with her young master and was offering counsel in private.
What if they thought Gideon was the voice of reason only to talk to her and realize nope-. The ninth is just two bickering teenagers with no adult supervision. Emperor help them all.
This would make Camilla's read in As Yet Unsent that she was "no older than 17" a lot funnier too tbh ajwoiejawoieg. The average person assuming at first Gideon is like mid 20s, versus Cam and Pal who saw her distressed and then heard her speak within a few minutes are like "oh that's a baby" lmao.
Bonus points too that Harrow is probably not even 5 feet tall and "was acutely aware she might be mistaken for younger." When they try to pass Nona as Harrow they borrow clothes from the smallest BoE member they can find and then cinch a lot of belts really tight to make those work. Gideon thinks Harrow looks no older than Jeannemary (14), Joli thinks Nona can't be more than 14 at most even as someone who's dealt with knobbly undergrown kids, and Hot Sauce (14) has an easier time passing for an adult at the broadcast than Nona. (And of course there's Mercy buying that she's 15 and reducing her age forever but you know.)
Imagine everyone thinking Harrow is probably around Isaac's age until they talk to her enough and even then they're not entirely sure. And looking at big mute brute Gideon like "Damn, she really has to put up with this brat." And surprise they're almost the same age and equally petty lmao.
(And then we get River Canaan where Ortus really just does have to put up with this kid, rest in peace.)
I do think Magnus could have guessed that Gideon was early 20s looking after a baby (4th house age) Harrow.
Gideon, to him, is an a stoic and principled ninth Cav off her planet for the first time and looking after her young necromancer. A damn good sword, protective and cool under pressure. He never realized Gideon was also a baby til the river.



















