The 41-year-old star has revealed he was the "lead bridesmaid" for his sibling Meredith's party, which saw him organise a trip for "17 women to Napa", reported Femalefirst.
Speaking about his wedding duties and party planning, Seacrest said, "I was the lead bridesmaid. I called my sister, 'What does it mean Man of Honour?' and she said, 'Well you've got to do everything a Maid of Honour would do.' I said, 'A bachelorette party?' She said, 'Yeah.' I said, 'Okay.'
Seacrest got "emotional" when his younger sister asked him to be her equivalent of a Maid of Honour in October last year.
"(She said) 'You've been by my side all of my life, and I wouldn't want you anywhere else, when I become a wife. I'm so lucky to have you as my brother, and couldn't imagine celebrating with any other. So basically what I'm trying to say... Will you be my Man of Honour on my special day?!'