Came across this as I'm still full of Ingo and Emmet brainrot. Well I think the 3 fav headcanons I have for either brothers are;

1. Ingo's lack of volume control (bro is shouting a lot without realziing it, kinda like me irl)

2. Both brothers tend to just gift others something random that just so happened to remind them of that person.

3. Ingo's the one who need a ton of caffeine to function throughout the day but it often backfires on him (caffeine withdrawal), meanwhile Emmet claims that caffeine makes him more sleepy than anything and naturally has a lot more energy.