The interactions would likely start with suspicion. The rogue avengers, having been through a lot, would be cautious. Peter, though, would be eager to connect. He might start by trying to help them in some small way. As they interact more, the rogue avengers could see Peter's potential and Peter could learn from their experiences. There could be moments of humor, like Peter making a joke that lightens the mood, and also serious discussions about their different views on heroism.
Yelena could bring a fresh perspective to the Avengers. Her skills as a Black Widow would be something they notice right away. She might start off being a bit stand - offish, but as she sees the Avengers' good intentions, she warms up. They could exchange combat techniques and strategies. And she might even teach them some of the more underhanded tactics she learned during her training.
It could be Hydra. They might be trying to take advantage of the split between the Avengers and the Rogue Avengers. They see Peter as a wild card and try to either capture or turn him against both groups.
Probably Steve Rogers. He has that all - American hero charm and he values loyalty and courage, which Peter clearly has. Steve would recognize those qualities in Peter right away and would want to get to know him better. He might see Peter as a symbol of the future of heroism and be eager to befriend him.
In such a fanfiction, the Rogue Avengers might initially be suspicious of Peter. They could test his loyalty and skills. Maybe Peter has to prove himself worthy to join their cause against the establishment Avengers. For example, he could show off his spider - powers in a unique way that impresses them.
One common theme is trust. Peter has to decide whether he can trust the rogue avengers, and vice versa. Another is the idea of family. The rogue avengers might see Peter as a new addition to their makeshift family. Also, there's often the theme of redemption, where the rogue avengers are trying to make up for their past actions through their interactions with Peter.
The Avengers would initially be in shock when they find out Peter is sick. Clint Barton would be the one to keep a calm head and start organizing things. Wanda Maximoff would try to use her powers to ease Peter's pain if possible. Vision would use his vast knowledge to try and find a solution. They would all be very concerned and do everything they can to make Peter better, from getting the best medical help to providing a safe and comfortable environment for him to recover.
The Avengers might react in different ways. Steve Rogers would probably be polite but firm in getting to know Peter's boyfriend. He'd want to ensure that he was a good influence on Peter. Thor, on the other hand, might be a bit more boisterous. He could either be really friendly and enthusiastic, or his loud and powerful presence might accidentally scare the boyfriend a bit.
There's a possibility that it's an old enemy of the Avengers who sees this as an opportunity. For example, Hydra could be involved. They might try to manipulate the situation to bring down both the rogue avengers and Peter Parker. They could spread false information to make the public turn against them all, while they carry out their own evil plans in the shadows.
They might be shocked at some of the dangerous situations Peter has been in without their knowledge. They could feel guilty for not being there to protect him more. And they would likely be very proud of his selfless acts.
If Peter was adopted by the Avengers, his relationship with Wanda Maximoff could be quite special. Wanda could help Peter understand and control his emotions better, especially when he's under stress during battles. Peter could also befriend Vision, and together they could explore the boundaries of science and magic. The Avengers would start to see Peter as a full - fledged member of the family. They would be more protective of him, and Peter would feel a stronger sense of belonging. His relationships would no longer be just about superhero partnerships but would be about real family connections. For example, they would celebrate holidays together and have family - style dinners, which would strengthen their bonds even more.