Wait, shouldn't Lyra's brother be called Eldarion, not Fredrick? The wiki (and the books, I seem to remember) says that Aragorn and Arwen (might want to add that too) had only one son, but several (unnamed) daughters (so Lyra would be one of these). 

Wow, I'm so picky...

 [url=http://lotr.wikia.com/wiki/Eldarion]Here's the wiki page[/url]