ETA: Accidentally wrote "corsage" instead of "boutonniere" in the title and can't edit it now- wrote it fast and now I can't edit it! :P
Here's a related question: what if they are not married? For instance, my FI's mother cheated on FI's dad years ago, and they divorced. Dad is now remarried. FI's mom has been single for years (talking 15+) and within the last year and a half got together with the guy she cheated on FI's dad with. He moved into her house. So, I get that FI's Dad, stepmom, and Mom get bouts & corsages, but what about the homewrecking boyfriend? It's already going to be awkward (they are NOT sitting together- separate tables)- I'm not sure what to do.
Related note- do siblings get corsages/bouts? My brother is walking me down the aisle (I want to give him one) and FI's sister is not in the wedding at all, but would she get a corsage?