I had a similar problem with an investment property and an ex-boyfriend. In my case, I had to find him and get him to sign the closing documents in order to sell it, so if your timeshare is deeded I would assume the same thing is necessary. These days with the Internet and stuff, I would think locating the other timeshare owner would be simple. If not, you may be able to place an 'Announcement' in a newspaper or something, but your best bet is to inquire with a professional or a lawyer that is familiar with real-estate laws in the area and ask him/her about this.

Hope this helps.

Jen