Here's a short fanfic that I came up with:
Peter had always been close with his dads, Tony and Steve, but as he grew older, he found himself struggling with separation anxiety whenever they had to go on a mission or even just leave the tower for a few hours.
Tony and Steve noticed this behavior and talked to the rest of the superfamily about it, knowing Peter needed more support than ever.
They all came up with a plan to help Peter work through his anxiety, even though it would be a process.
One day, when Tony and Steve had to leave for a mission again, they sat Peter down and gave him a list of fun activities to do while they were gone.
"You can work on the computer designing new technology with your Uncle Bruce, or you can practice your archery with Uncle Clint," Tony said, patting Peter's knee reassuringly.
"We'll be back before you know it," Steve added, ruffling his hair.
Peter nodded, but he could feel his heart clenched in his chest. He knew they cared about him, but being away from his dads for any period was scary for him.
As the pair suited up and boarded their transport, they could see the distress on Peter's face and they both felt terrible for having to leave him alone.
But the superfamily rallied around Peter and found ways to keep him occupied and distracted. They spent more time with him, included him in their daily activities, and even allowed him to come on some of the less dangerous missions.
Slowly but surely, Peter's anxiety began to lessen. He started to understand that his dads and the rest of the superfamily will always come back to him and that he had a support system that he could count on.
The next time Tony and Steve went on a mission, Peter was better equipped to handle their absence. He began to look forward to the activities he would do with the rest of the family, and his anxiety became less and less of a hindrance to his everyday life.
When Tony and Steve returned to the tower, they were relieved to see how much their son had progressed. They greeted him with hugs and kisses, telling him how proud they were of him.
With the support of his dads and the superfamily, Peter knew that he could overcome whatever obstacles came his way in life.
I hope that you liked it!