Bruce would probably be more analytical. He might wonder how Tony's marriage could affect his work and the team. He could also be curious about Tony's relationship dynamics. Meanwhile, Wanda might sense the emotions involved, like Tony's happiness or any underlying stress in the relationship. And Rhodey would likely be supportive, since he's Tony's close friend. He might even help Tony deal with any potential issues that come up with the Avengers' reactions.
Thor could be angry. He's a proud warrior and being kicked out like that might be seen as an insult. He might even challenge Tony in some way, either verbally or physically. However, he also has a sense of honor and might listen to Tony's reasons if given the chance.
In many fanfictions, the Avengers' reactions vary. Tony Stark might be proud, like he's found a protege. He'd probably start upgrading Peter's suit right away. Captain America, on the other hand, would be more concerned about Peter's moral compass and whether he's ready to be a full - fledged Avenger. Hulk might not care much at first, but once he sees Peter's strength, he could become his ally. Overall, it's a mix of different emotions and actions.
They might be shocked and confused. It could lead to a lot of internal conflict and soul-searching among the team.
The Avengers finding out Tony is married in fanfiction could create a whole new set of storylines. For example, if Tony's marriage was a result of some kind of arranged situation, the Avengers might get involved in trying to figure out if it's a good or bad thing for Tony. Or if his spouse has a hidden power or identity, it could bring danger to the team, and they'd have to deal with that. There could also be relationship drama within the team, like jealousy from a character who has an unrequited love for Tony. This discovery could be a catalyst for many different plot twists and character developments.
They could react with surprise. After all, Peter is still young. But then they would likely be happy for him. Maybe they'd offer to take MJ out for a nice dinner to get to know her better.
Peter might be really nervous at first. He's used to being just the friendly neighborhood Spider - Man, and now the Avengers know he's Tony's son. He could be worried about living up to their expectations.
The Avengers as a whole would probably start to work with Daredevil more closely. They would realize that his blindness doesn't make him any less of a hero. They would also learn from his unique fighting style which is adapted to his lack of sight, and they might incorporate some of his techniques into their own combat strategies.
They would react differently. Tony might be a bit embarrassed but also secretly pleased. The others, like Thor, would probably be very curious and want to read some of it.
Thor would be quite confused at first. Fanfiction is not something from Asgard. But once he gets the gist, he might say something like 'This is a strange Midgardian custom, but if it shows the great friendship of Steve and Bucky, then it is not all bad.' Meanwhile, Tony would be all over Steve, making snarky comments and asking if he's finally going to admit to some hidden feelings for Bucky according to the fanfiction.
The Avengers may become more empathetic. Learning about Tony's family issues or his unspoken fears through fanfiction could make them understand his sometimes difficult behavior better. They might start to cut him some slack when he acts brashly, realizing there are underlying reasons for it.