"I looked! The closest thing I found was that dancing hex but my mum already tried that and I fall over just like I would if I tried to dance normally. ...Which I guess makes it a little less useful on me than it is on most people in some ways? Since I can aim from the floor better than I could if I were jigging."

"Can most people hexed that way not fall over even if they want to?"

"I think they can't overbalance on purpose in a way that isn't dancey. Do you want me to hex you and see?"

"Yeah, definitely!"

So she aims her (non-overpowered) wand at him and says, "Tarantallegra!"

And it turns out he can overbalance on purpose but it takes some doing, one rather instinctively tries to stop oneself from falling and this is still true while hexed.

"All right, so if you're ever dueling somebody you can fling yourself to the floor if you need to stop dancing around."

"Good to know! I don't expect to ever be dueling somebody, if somebody insulted me I think I wouldn't mind and if they insulted the family Theodore'd be quicker to it."

"And if they just outright challenge you to a duel?"

"Then I suppose I'd have a duel, but I don't expect that to happen? I don't go around insulting people who aren't not my cousins."

"...aren't not your cousins?"

"The other Ways. I do a lot of pointless glaring at them. I don't expect it to result in a duel."

"I have noticed you pointlessly glaring at them and them not dueling you about it."

"There you go!"

"Is there a reason you make sure you don't say you're cousins, specifically, instead of just having cousins who you glare at?"

"It would be inaccurate."

"...really?"

"They're my grandfather's grandchildren by his second marriage. That's only half-cousins, at best."

"That's more related than, like, third cousins, which are still a kind of cousin."

"Well, brothers are more related than third cousins, but you wouldn't call them cousins, because it'd be inaccurate. Also practically everyone here except you is my third cousin or closer."

"...because brothers aren't any adjective of cousins."

"I have cousins. On mum's side. And then I have not-cousins, which are all the Ways. That's just how it is."

...oooookay.

Yup.

"...so why do you pointlessly glare at them? It's not their fault that they're your half-cousins."