Durin is not a child in my opinion
P/s: English is not my first language so I'm sorry if I make any mistakes
I don't think that he is a child, newborn, or minors at all.
The only people who actually called him "child" are Venti and Anderdotters. Venti called everyone in Monds as 'children', even Dvalin, who is a grown dragon, even from way back then. Anderdotter is obvious because she's his mom (Mini Durin)
We don't know when OG Durin was made, but we do know that he is older than Albedo. Proof is Gold uses him as her failed experiment disposal, one of them is Subject 2. And we don't know how old he was when she released him.
Mini Durin is not his real body, he just changed it so he can fit in with the villagers. He was that big dragon before, but because he was too big and clumsy that's why he was cast away.
We don't know when An passed, but she is part of the Hexenzirkel and a mortal, so she must have passed hundreds of years ago. That will mean we don't know how long Mini Durin was in the Simulanka.
People like to bring up how he acts like a child in Simulanka. For me, he acts immature and childish, but not like a literal child. Remember, he was in the Simulanka, which is a storybook for children, so yes, there is an explanation as to why he acts childishly. Even the adult villagers all act the same way. Because it's literally a storybook like a fairytale
People bring up the two weapons. I read through it. One doesn't mention anywhere that he is a child, just that he thought he was having fun, but he was actually destroying things. The second weapon is the Festering Desire. People point to a single line that reads "This is a memory, a memory that a child named Durin had of his mother" and think it proves he is a child. But no, this story is about a mother and her child. They use 'child' because this is their relationship. A mom and her child
The current human Durin is not entirely Mini Durin. In 5.6, it is revealed that Subject Two was absorbed back into Durin. Durin will be awakened again. OG Durin was a gentle dragon, but because of years of solitude, abyssal corruption, AND the memory+resentment toward Albedo from Subject 2 (I think some people forgot that Durin gained the knowledge and memory of Susbedo after Sus was reabsorbed), Durin was twisted into an evil dragon. That's why Albedo figures that if he combines OG Durin with Ander's Durin (aka Mini Durin), with the hope that Mini Durin's pure and gentle nature will be able to override that. And two will exist as one person, aka The current Durin (Let's call him Human Durin)
The current Human Durin doesn't act anything remotely close to a child at all, he's shy because he have never actually interact with normal people before and remember he is both OG and Mini (if we count subject two too then it'll be three) both Durin have not actually confirmed to be a child anywhere beside Venti and Anderdotters whom I already explained above. He's smart, he knows what he is doing, he's not some baby that need to be protected, he have subject two knowledge and memory because it was also revealed that Subject two was alive the entire time (500 years) not only that OG Durin was older than Albedo so he must have seen Gold performed alchemy. In the story quest, I would argue that Durin acts a lot more mature and even has to stop his brother from yapping too much and just get to the point.
People bring up the whole "Hey, kid" from Jahoda. But here is the thing....Jahoda called him "Onii-san" in JP....unless you're telling me "Onii-san" means "kid" somehow? In Kr, it doesn't mention what she addresses him as. In CN, she called him "ĺ°ĺĽ" (yes, I actually went to Bilibili for this). I research what it means. Apparently, if you are close, as in familiar or family, it would mean "younger brother," but if you are a strangers or not close, then it would mean "Young Man/Young Fellow" which is what Jahoda and Durin relationship is.
A lot said "Well, young man means he's a teen" No?? Young Man can literally be used for anywhere between 15 to 25 or even early 30s in some places. In Genshin Impact, Ororon is called a "Young Man" you can't tell me that Ororon is a minor. In the story quest, VARKA called Durin a "Young Man" too
Some people actually said "Well he uses a short male model so he must still be a kid like Bennett, and his voice sounds young too" Hello? What about the other short males? He doesn't look anything like a child; he doesn't even act childish. I would argue that Dahlia sounds even younger than Durin and that man loves to get drunk with Venti (Venti also sound young btw. It depend on the VA) Also, Bennett is not a child either, he was proven to be in his 20s with the Mare Jivari quest.
Some other things that I notice are his dripmarkets. People only look at the first and forget the second. The "evidence" that people point to is the words "Horned youth" and believe that's the proof. Again, just like "Young Man" Youth can mean anywhere between 15 and 25.
The second dripmarket said he embarrassed himself at the Tavern and I think....why can't it be anywhere else? The Knight Of Favonius, The Cathedral, Good Hunter? Or heck, even Albedo research lab all the way up the mountain, maybe he messed up while helping and embarrassed himself there, literally anywhere else would be more believable, but I checked every single dripmarket from different languages and it's always the freaking Tavern. Why does it have to be a Tavern? An adult place. Listen, I know that Taven can serve non-alcoholic drink too. But that's not all, he was able to order his own drink at a Bar in the story quest, and I know "That bar has non-alcoholic drinks". But I do think it's weird that this supposed "kid" was mentioned anywhere near adult places twice. Even his brother, Albedo, whom people believe is an adult, and he is! But Albedo never got mentioned anywhere near those places. Also, Albedo is called a Teen Prodigy too if I'm not mistaken, and no one thinks he's a kid. Btw, just because those places do serve non-alcoholic drinks, doesn't fully mean he's a child either. We need to look at the full context here, A tavern and Bar are adult places, it mostly for adult even if they have non-alcoholic drinks, so we can't use that to "prove" he is a child either. That's like saying people who went to Chuck E Cheese (primarily for kid) they also serves beer, means that Chuck E Cheese is for adult. That doesn't make sense.
I saw on X that people use the excuse to say that in Germany, people can drink alcohol at 16. First, Mondstadt is not Germany, yes, Hoyo takes inspiration, but it's not completely Germany either. Not only that Genshin Impact rated 12+, but it's also from a Chinese company. And we all know how crazy censorship in China is. Do you really think Hoyo would put a minor drinking alcohol in Genshin Impact? The drinking age in China is 18. Selling or drinking is NOT allowed. Diona is different, she sells drinks for adults, she DOES NOT drink them. I don't think Hoyo would risk showing or mentioning an actual minors drinking alcohol especially a 12+ rated game like Genshin
Another thing people said was that he just got his new body so he practically a baby. Well in that case, Ineffa is a baby too because Aino found her and make her the current body. Do you see how weird that is? Unless you're telling me that Aino is an adult like Dori who can drink alcohol, then you can confirm that Durin is a child but Aino, from the story so far beside her brilliant mind, she still act, behaved and talk like a child. Meaning, we can't use that to say he is a child either. His body is new but his name, memories is very very old by now
The only minors in the game are Noelle, Fischl, Klee, Qiqi, Diona, Aino, Yaoyao, Kachina and maybe Razor. And I'm not saying it's fine to goon for the other like Nahida or Dori because they literally look like children and have a baby model. But Durin doesn't use a baby model, he uses a short male model and you can't say "Oh Hoyo is just lazy" no with all the points I give out above, there are reasons why they don't use a baby model for him because he is not a kid. Just like all the short male models, none of them are proven to be children either, even Razor (I just can't find reason to point either he is a kid or an adult). And before you think Chongyun, Xinqiu, Gaming, Freminet, Mika, Bennett aren't children either. Chongyun is proven to be able to drink alcohol and was drunk for a while in a past event, Xinqiu is his best friend so they would be around the same age, Mika can drink he just said he gets drunk really fast, Freminet is a bit more difficult but if we look at Arlecchino quest and calculate a bit then Freminet would come out at between 18 and 19, Gaming's whole story from the Lantern rite was growing up and moving out, he got a job and pay his own bill. Diona has a job, too, BUT she still stays with her dad. Bennett was born in the Mare Jivari and was discovered shortly after. In the quest, it is mentioned that the Mare Jivari disappeared 20 years ago, meaning Bennett is at least 20 years old.
(Edited) I want to add another small thing. OG Durin and Mini Durin are NOT the same dragon. Both are created by different people. Anderdotters created her Durin based on the real Durin to "give him a better ending" so they mirror each other but not completely the same. If Anderdotters created Mini Durin based on the OG Durin that would mean both of them were isolated for who know how long. Gold isolated her Durin for who know how long until she released him. Mini Durin too was isolated so that's another reason as to why both of them act the way they do i.e naive and childish
So that's my opinion as to what I think about Durin. I get that some people feel the sense of witnessing him growing up, but for me and for some others, I have never seen him as a child, even Mini Durin. I saw him as a creature with no age attached.
So if you want to write smut or fanfic for him. I'd say go ahead because, like I said above, there is no legitimate proof that he is a child, and the "proof" that people said can be explained so easily.
And please let us all be respectful of others' ideas. If you don't like something like this and are still convinced that he is a child, that's your own thing, and, like I said, let's be respectful because yours is not 100% either and so stroll away, ignore it, no need to go all crazy over those that have a different view than you
That's all I have to say about this whole Durin thing. Sorry if I make any grammar mistakes, English is not my first language but I do hope my words are easy to understand to you. Of course I am open to anything idea and refute but please be respectful. Goodbye and Thank you for taking the time time to read!