Yeah, I was thinking the same thing as Andro. When I was younger, there were two Gemma's in the class. Although we/the teacher didn't use each others middle names, it probably would have been easier to do so. I've also known friends who prefer to be known as their middle names because they didn't like their first names as much.

My middle name is Sarah-Anne or Saranna (I prefer Sarah-Anne). My great-grandmother was called Sarah-Anne, and so I was named after her.