I assume you are asking about the beginning of Book 4 and not about the beginning of the whole epic.  No one is getting married at the beginning of the Odyssey as a whole.

At the beginning of Book 4, many people are gathered at the palace of King Menelaus.  Both of his children, Megapenthes (a man) and Hermione are getting married (not to each other).

Their wedding feasts are an opportunity for the people present to reminisce about the Trojan War (Helen, wife of Menelaus, was the cause of the Trojan War and she talks about her experiences) and about Odysseus.