Hey,
Luke Ruprecht Skywalker is a good name. :D But yeah, middle names are pretty rare in fiction, probably partially because they hardly ever come up in everyday conversation. Or even non-everyday conversation. And sci-fi fantasy it'd be even weirder to see a middle name, since they're hardly universal.
Not sure if it'll have what you want, but there was another discussion on middle names a whiles ago,
http://www.behindthename.com/wwwboardarc/messages/4684.html. And
Nanaea gave this url [
http://www.firmament.com/genealog/howname.htm] to someone else who asked, I think the site has some info on middle names' origins.