In some cases it's just their godparent's names tucked on. I went to school with a guy who had five given names - his own, and four godparents. Nobody used anything but his own given name.
But then you've also those horrid parents who project their own wish to be a special little princess different than everyone else onto their child, and because the poor kid has to stand out from all the others they give them abominable names. Seraphy still got relatively lucky and just has a long-ass name that can easily be abbreviated once she has the guts to defy her mother in that.
Other kids get really unlucky and either get something that just isn't a name at all (think "Cheeseburger" or "Dispenser"), an intentional misspelling of a word (the subreddit for horrible names, /r/tragedeigh, is named after one of those examples), or worst case, both of it.