1. Worm Loves Worm by J.J. Austrian
Plot Summary: When a worm meets a special worm and they fall in love, you know what happens next: They get married! But their friends want to know—who will wear the dress? And who will wear the tux? The answer is: It doesn't matter. Because worm loves worm.
Youtube read aloud: https://www.youtube.com/watch?v=1A78frDhJsc
Featured by Horn Books as a top LGBTQ picture book in 2017, this is an adorably gender neutral book about two worms preparing their wedding. No one has pronouns and thus could be any gender. The worms end up being both bride and groom, wearing half the dress and half the tux each. The language is pretty simple in this book and thus easy for younger kids to understand.