The groom told his sister-in-law that he's had romantic feelings for her 'for a few years' shortly after she helped his fiancée pick out her wedding dress
"A flower girl spreads petals and sets the stage for love, growth and commitment, which my grandma has done for me my whole life," bride Katie Lopus tells PEOPLE
"I don’t think anyone else will ever be able to say they got to marry the love of their life by a big Cheez-It in front of 50,000 people!" the groom tells PEOPLE