Having kids with Levi headcanons (Canon Universe)
Imagine having two kids (twins or not, both works) with Levi sounds all good and wholesome. Until you realize just how much you underestimated Levi's genes. Like damn, these are toddlers and you'd be all over the place just to watch them not hurt themselves playing. Mind you, these kids, are Ackerman kids. They have as much energy as their father. More so since well kids being kids. You'd have to match their energy or you'd be left in the dust. I don't mean that they'd be like monsters (maybe?), but they'll sure be a menace to babysit. And that's just for when you guys are at home. Imagine if you need to work. Just imagine if you guys are at a family outing in a park, where there's people around. God just pray that you won't lose sight of them the second you just try snack on something, talk to Levi, or just buy something in one of the stalls. You'd miss one of them, worse, both of them if you're the only one taking them out. If you're with Levi, well he's not perfect and there are definitely times for when he missed one of them or both of them. Immediately bringing them back to where you are or where you guys are supposed to be seated.
Unless well you turn out to be one heck of a goddess at babysitting kids then all the better. And this is why when the kids grew up to like five or older, more often than not. You and Levi would have to teach them how to properly behave. And as years pass, teaching them became a little harder, but it has it's own rewards. Naturally, as they grow older, methods on teaching them proper behavior adjust accordingly as well. Yes, I know Levi mentioned that "Pain is the best kind of discipline," but this is more likely because it's being applied, to Eren a soldier like he is, who also has a stubborn attitude. Not to mention, a titan shifter who's limbs regenerate like a lizard. That's him as a captain, as a superior officer. But he's a bit more gentle as a father. Especially as a father to his kids with you. He's stern, one quality that's never removed from him. Sometimes a little intimidating. And sometimes, you would be the balancer of sorts to his intimidating nature when teaching your kids to behave. It's a long process, but it works for both of you, Levi, and your little family with him.