Communion (Noun)- an act or instance of sharing

https://www.merriam-webster.com/dictionary/communion

” It was a communion based, in some odd way, on a set of shared separations: Everyone was here for reasons of their own.” – Walk With Me

My understanding of the word, as used in the sentence would be that, everyone was sharing one thing in common and that was that they’re all here for a purpose but that may vary for each individual.

They’re all gathered in communion of the bride and groom’s wedding day.