There are programs you can sign up for if you are part of the LGBTQ+ getting married/big event and you have no one to support you/walk you down - basicly be your stand in family cause you don't have people who are willing to be there
( it's a really good organization, and I recommend looking up Stand In Pride )
So Peter uses this program
Option 1) Either everyone in the family is dead
Option 2) Go for homophobic Aunt May
And he gets paired up with Tony Stark who grew up with a father that looked down on his non heterosexual and his Father never went to any major event so he wanted to stand in for people so they don't feel alone. He keeps this on the downlow, NDA's signed that they can't talk about him standing in but free to share the videos/photos
Depending on the route you wanna go
Option A) it's for Peter's College graduation
Option B) it's for Peter's Wedding