Damn it! I wish I understood how these polls work. I didn't know that I could choose multiple categories, so I selected 'other', meaning 'all of the above'. This means I probably could've voted multiple time in Master13's other poll, as well. Argh!
Anyway, my most common people to fantasize about are friends/acquaintances, followed by celebrities. Invented characters appear with some frequency, though usually as Dommes rather than subs. Relatives and fictional characters make the odd appearance here and there, but rarely as a focus of activity.
This was an interesting question to ask; I'd never really thought hard about it before.