As the article says, they will forward it the email the user signed up with, which is of course required to use Facebook so your relatives must have one (even if they don't check it).
And now ask yourself a question why would they want to do that? I mean why keep unneeded load on their servers and support whole infrastructure just to forward e-mail. Probably because they want to continue to reading your e-mails but now they don't have to invest into storage. Just copy the interesting ones for themselves.
