I had to scrounge bridesmaids because Pedro has three brothers and a best friend. He also felt strongly about including my brother on his side, as well -- so he had five guys total. He avoided the best-man conflict by asking his youngest brother -- who was then sixteen -- to be the best man. None of his older brothers were going to question that.
I asked his sister, my brother's wife, my cousin, my best friend (who I've known since I was seven), and my college roommate. I would have asked my high-school best friend instead of my cousin, but she was living in Europe at the time and had a ten month old baby. I didn't know if she'd be able to come to the wedding at all (she did), so I felt asking her to be a bridesmaid would have been an undue burden. Honestly, though, as long as his sister, my sister-in-law, and my best friend were included, I couldn't have cared less about anyone else. I actually felt kind of bad asking College Roommate and Younger Cousin to act as "filler." They seemed cool with it, though.
The rest of the guys -- assorted cousins, et cetera -- were ushers. I asked several of my female cousins to sing -- they have lovely voices and one of them actually sang professionally for weddings and such when she was in college, so it was perfectly appropriate. We asked our Dads to do scripture readings. My mom's oldest sister played piano and a close grade-school friend of mine played harp. My nephew was ring bearer, my niece was flower girl, and my cousin's son was the flower girl's escort. So there were a lot of people included that weren't part of the official wedding party. They all came to the rehearsal dinner and we had a nice time.
My sister-in-law, who just got married this past July, flouted tradition by asking her four brothers and the unnoffficial "sixth Dunston" (Pedro's best friend, who lived with their family for a while after high school) to stand up with her. She also had her husband's sister as maid of honor. So all told, they had six groomsmen, a maid of honor, and five "bridesmen." It was pretty cool.