This is not common, but these aren't the first parents to name a girl
Gavin (or Gavyn), as exemplified by the following recent article in the
Los Angeles Times about a lesbian couple whose 15-year-old daughter is named
Gavin:
http://www.latimes.com/news/local/la-me-gaykids16oct16,1,7672369.story?ctrack=1&cset=true