Their relationship would develop through shared experiences. For instance, they could go on missions together where they have to rely on each other's skills. Peter's quick thinking and agility combined with Tony's technology and experience would make them a great team. As they face challenges together, they would grow closer. Tony would start to see Peter as the son he never had, and Peter would find in Tony the father figure he was missing. There would also be moments of fun and relaxation between them, like when they tinker with new gadgets in the lab or when Tony takes Peter flying in the Iron Man suit just for the fun of it.
Their relationship could develop in a mentor - mentee way at first. Tony would teach Peter about science, technology, and how to be a better superhero. As time goes by, they would become more like father and son. Peter would start to look up to Tony not just as Iron Man, but as a dad. For example, they might have movie nights together or Tony would help Peter with his school projects.
At the beginning, their relationship might be a bit rocky. Peter is used to his own way of doing things and Tony has his own ideas about how a superhero should be. But as they spend more time together, they would learn to understand and respect each other. Tony could introduce Peter to the wider world of superheroes and politics within that world. Peter, in turn, would bring a sense of youthful innocence and new ideas to Tony's life. They might also have some disagreements along the way, like when Peter wants to take on a more dangerous mission than Tony thinks he's ready for, but these disagreements would only strengthen their bond in the long run.