Lover Romeo

You actually can, unless they're someone very important on Runescape, like someone on the first page of the high scores, well-known moderators, etc

 

They were talking about the 'display name', you know the way that name changing is possible? He would still have the login(unseen) Lover Romeo, but someone else could take it as a display(the name that is 'seen', ingame/highscores/etc. if he didn't change back in time.

About the only other case someone else couldn't have it would be if Jagex personally 'holds it hostage', like they have with some of the more famous players, perm deleted names, and such.