I just want the three talking and discovering that High School wasn't much fun for either of them (doesn't necessarily have to because bullying or anything actually happening in HS but could also be family problems that just manifested in that time).
It doesn't have to be super-dark (mostly here for the bonding part) but if that's anybody's headcanon go for it.
Bonus for at least one of them assuming that the others must have had a great time in high school.