School Mates
You have a special bond with people who graduated the same year as you that you just don’t have with anyone else. Even if you don’t like any of your classmates at all, there will still be a strange sort of bond between you all, based simply on you all going through these formative years and experiences together.

This is an interesting and thought-provoking fact of life. But if you want to turn it into a slightly squicky fact of life, you can think about it as this person did! There’s a weird mental image that I never wanted to have of all of my high school friends’ parents.