Facebook messages re-read?

[Who Knows]

Okay so you know how on Facebook it shows that you have read a message, my sister was showing me that her ex-boyfriend had recently read a message that she sent him 3 months ago. It had already came up that he read it 3 months ago when it had been sent. What does this mean? Is he re-reading the messages? Thanks for any help!

[Access Denied]

you can make your facebook messages "mark as unread" after reading. And read them later. I guess he did the same thing. :-)