Percy and Steve Rogers would likely have a relationship based on mutual respect. Steve would admire Percy's courage and loyalty, which are qualities he values highly. Percy, on the other hand, would look up to Steve as a great leader. And with Bruce Banner, Percy might be a bit in awe of Bruce's scientific genius, while Bruce could be intrigued by Percy's demigod biology and how it differs from normal human physiology.
Percy would probably have a really interesting relationship with Thor. They both have connections to powerful elements, Percy with water and Thor with lightning. They could bond over their experiences with super - powered abilities. With Natasha, she might take Percy under her wing and train him in some spy - like skills, since he's now part of the Avengers 'family'.