www.thepeerage.com has almost everyone. Awfully designed site so go onto google, type in the name followed by 'site:thepeerage.com'
Also go to a library and pick up a copy of People of Today, Who's Who etc.
Burke's peerage is the definitive guide on the aristocracy. They print hard copies, also available at any major library.
Full title: Burke's Peerage Baronetage & Knightage, 107th Edition: Clan Chiefs, Scottish Feudal Barons (Burke's Peerage, Baronetage and Knightage)
Or you can search for people here
http://www.burkes-peerage.net/ but you have to subscribe to view the actual records.
Most titles will also be on wikipedia because there exist a large number of eccentrics who are obsessed with the aristocracy.
You'll be able to find out the lineage of anyone titled and hence deduce how long it has been in the family. It will also tell you for what it was issued and usually by whom (i.e. which monarch)