They would be all over him! Steve would probably have a big, warm smile on his face and just be in awe of how small and precious he is. Clint would make silly faces to make the baby laugh. Bruce might be a bit more cautious at first, but then he'd be charmed by Peter's little giggles.
Since he might be related to Tony Stark, there could be an emotional connection for the other Avengers. They might feel a sense of obligation to protect him or guide him, which changes their group dynamic. For example, Captain America might take on a more father - figure role towards Peter. Also, his presence could create some jealousy or competition among the Avengers who want to be his mentor or closest ally.
There's a fanfic named 'Peter Stark and the Avengers: A New Alliance'. In it, Peter Stark might bring a fresh perspective to the Avengers. He could be the one to solve a complex problem that the Avengers have been struggling with using his unique intellect. Maybe he comes up with a new strategy to defeat a powerful enemy that the Avengers hadn't considered before. Fanfics like these often explore the relationships between the established Avengers characters and this new, interesting addition of Peter Stark.
Maybe in the fanfiction, the Avengers initially think Peter Stark is just a regular kid related to Tony Stark, but then they find out he has the ability to time - travel. This would completely shift the story as they would have to deal with the implications of time manipulation and how it affects their missions and relationships.
Obviously, baby Peter would be one of the main characters. Among the rogue Avengers, it could be Captain America if he goes rogue in the story. Hawkeye might also be there as he has a family - like side and could be sympathetic to baby Peter. And Scarlet Witch could be involved too, with her powerful magic.
In this fanfiction, perhaps the rogue Avengers are hiding out when they hear baby Peter crying. They initially think it's a trap but then realize it's just an innocent baby. Some of the Avengers might want to take him with them because they see his potential, while others are more hesitant due to their own precarious situation.
Well, the plot could be really cute. Maybe the Avengers are all shocked when they first see baby Peter Stark. Tony, being the proud father, shows off his baby to the team. They might all take turns holding the baby and trying to make him laugh. And perhaps Peter, even as a baby, shows some signs of his future genius, like being fascinated by some of the Avengers' high - tech gadgets.
There could also be a scenario where the Avengers travel back in time to seek Howard Stark's help. Maybe they need his unique insights on some ancient technology or a threat that has roots in his era. So they go back in time and encounter him.
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.
I think Thor could be really excited too. Thor loves a good warrior and Peter, with his spider - like abilities, would be an interesting addition to his view of heroes. Thor might be amused by Peter's small - scale heroics compared to his own grand battles and would enjoy seeing Peter's potential grow.