What is your opinion on Percy, Jason and Nico often being depicted as really close friends and\or brotherly (personally, i disagree with it because of how Jason treated Nico before the Cupid scene and I think Nico and Percy's relationship is too complex to fix)
YES! Finally someone that see that too!
While I don't really criticize people who see their relationship in that way,or HC that they are extremely close,like cousins/brothers should be,I also don't agree with it.
Nico and Jason relationship started in an horrible way,and while characters development is a thing,I don't like how Jason tried to be Nico's friend. I already talked it in another post,when I talked about how the Seven where horrible to him. The guy started to be ok with Nico only after Cupid forced him into a traumatic experience,and tried to be his friend only afterwards. I know that in ToA they are proprably closer and I also know that Nico took his death pretty hard because "Jason was Nico's first friend". And while I don't go against canon,I think Rick was wrong with this. They weren't never that close,during HoO: After Cupid Jason wanted to,but Nico was still a little wary of him in HoH; and when they met again in BoO,Nico ditched him for Will,2 times,and Will was almost a stranger to him. While Jason had a good character development,and Nico kinda of accepted him as his friend in the end,their change of dynamic was forced since it happened in only 40 pages,which isn't that much. They didn't have a a gradual improvement to solidify their relationship,just Jason that went from "I don't trust you." to "Let's be friends!" .I don't think they would be that close and people need to acknowledge that. While you can write whatever you want (it's called fan-fiction for a reason after all),you also can't change the fact that those two aren't the best of cousins. And Rick shouldn't present their relationship as "best friends forever",because they are not. If Cupid didn't happened Jason would still be horrible to him. You know who was really Nico's first friend? That was there to help him in his worst,and even after witnessing his traumatic life,stayed? Reyna. Not Jason. And he also fucked up with her when he made her join the Hunt.
Talking about Nico and Percy relationship is like opening Pandora's Box. I already said multiple time how I love their "love-hate dynamic",and how it's done pretty right with them. But again,there is so much trauma with them and they will be properly hunted by it forever. They also tend to blame each other for things that they have no control over,and at the same time,they will do everything to help each other. And again,while characters development is a thing,it will never work that good with them. There is just so much to deal with. They should have therapy sessions together with Mr.D,if not for their traumas in Tartarus,then for their friendship. They can be there when the other needs help,sure,but at the same time they will never be comfortable that much with each other. That train is long gone and will never come back. They try to make things work but it's pretty awkward between them since they clutch to that last part of friendship,trying to rebuild it,but it never work. And it kinda sucks because they would have a great relationship. They are just too complex to be the "inseparable chaotic duo of greek Big 3 children" that the fandom like to see in them.
Actually most of the Big 3 children,realistically and canonically,are awkward with each other. Thalia and Percy for their fathers's rivalry and the fact that when Thalia come back,everyone treated Percy shit,while Thalia had to see herself "replaced" in Annabeth's life by Percy. Thalia and Nico will never have a good relationship with each other no metter what,Bianca's death is too heavy for both of them to overcome,even if they tried in BoO (Rick could give us something of them but he didn't,another occasion ruined). Jason and Percy were compared to each other during their amnesiac time in their respective Camp,putting this alongside the fact that they didn't know each other (no,they also aren't that much of a "bros" that people make them to be) and their parents rivalry,with their one,isn't a good match. I already talked about their relationships with Nico. Hazel will forever be hunted by her insecurities of being a replacement for Bianca in Nico's life,while he doesn't know anything about it. Thalia will forever feel guilty about Jason's early years of life,and Jason probably will never get all of his memories back about their family. Hazel and Thalia don't know each other,and she has a good relationship with Percy and Jason,so she is saved from them (for now).
Rick is good at wrinting complex relationship,the problem start when he tries to resolve them with "and they were best friends!" when they can't. I don't see Nico being that close with either of his cousins because of that went down with each of them (that's why headcanon exist for,of course,since we can't have what we want in the canon narrative). Percy might be the only exception,but still,they will be complicate with each other.
And again,I don't have anything against headcanons that people have of their closeness,they are completely ok,I also want the big 3 children to be chaos gremlin together and I love when fanfictions portray them in that way. I hc Thalia,Percy and Nico in that way too,since Rick didn't give us much of their dynamics (without the trauma),and that little we had give us potential for some crazy quests and moments. But we need to separate the canon narrative from a fantasy we fabricated when we talk about the actual characters in a canon setting.