I think this kind of fanfic can be quite controversial. In the Avengers universe, Steve and Tony have a complex relationship, and adding such a plot of 'cheating' with Bucky can change the whole dynamic. Some fans might like it for the drama it creates, but others might feel it goes against the original spirit of the characters' relationships.
Well, from a story - telling perspective, this fanfic could be interesting. It takes the well - known characters of Steve, Tony and Bucky and throws in a completely unexpected twist. However, it also might make some fans uncomfortable as Steve is often seen as a morally upright character. So it really depends on the reader's taste whether they can accept this new take on the characters' relationships.
The fanfic alters the perception of the characters in multiple ways. Steve's reputation as a trustworthy and noble character is at stake. His actions of 'cheating' are not in line with what fans usually expect from him. Tony, who already has a complex personality, now has another layer of being wronged added to his character. Bucky, who has his own set of issues in the official stories, is now part of this love triangle that further complicates his image. It shows how fanfics can reshape the understanding of beloved characters in unexpected ways.
One possible reaction could be Tony's heartbreak. He might feel betrayed and angry, leading to a rift in his relationship with Steve. He could also become distrustful of others in the future.
Tony might cut off his relationship with Steve completely. He's a proud man and wouldn't tolerate such betrayal easily.
One way could be through communication. Steve could come clean to Tony about his feelings for Bucky and apologize sincerely. Tony might be able to forgive Steve over time if he sees that Steve is truly remorseful.
One possible scenario in this fanfic could be that Bucky and Steve notice Tony is overworking. So they start by making sure he eats regularly. Steve might cook his old - fashioned but hearty meals, while Bucky keeps Tony company during meal times to make sure he actually eats. They also likely limit his access to the workshop for a while, to force him to rest. Maybe they set up a little relaxation area in Tony's living quarters with comfortable chairs and soft music.
One common theme is protection. Bucky and Steve often see Tony as someone who needs safeguarding, whether it's from physical threats during missions or from the emotional harm caused by his past. For example, in many fics, they'll stand up for Tony when others in the Avengers question his motives.
The theme of sacrifice is also quite common. They are often put in situations where they have to sacrifice something for the greater good or for each other. For example, in some fanfics, Steve might sacrifice his own safety to protect Tony or vice versa. And a lot of fanfics also explore the theme of trust. They start with a lack of trust due to their different personalities and views, but as the story progresses, they learn to trust each other more.
At first, it might be a bit rocky. Tony, being used to his own space, might feel smothered by Steve and Bucky's over - protectiveness. But as time goes on, he'll start to see their good intentions. Steve's moral compass will inspire Tony to be a better person, and Bucky's loyalty will make Tony feel secure. Eventually, they'll become like a real family, with Tony looking up to Steve as a father figure and seeing Bucky as a cool older brother.
One great 'bucky and steve care for tony fanfic' is 'Healing Hearts'. In this fic, Bucky and Steve notice Tony's struggle with post - battle trauma. They start by simply being there for him during his nightmares, bringing him warm milk and sitting with him until he calms down. Their care gradually extends to helping him in the lab, understanding his projects, and protecting him from those who might want to harm him for his tech.
Friendship is a very common theme. Despite their differences, they come together and form a strong bond. Another theme is redemption. For example, Bucky might be seeking redemption for his past actions, and Tony and Steve play a role in that process.