Answer:
Most but not all inbreds are sterile. It depends on how much incest is in the family. In fact even idiots who marry first or second cousins can wipe out a whole blood line. but that's for the best isn't it... you don't really want these genetically screwed up people who choose to breed to pass on these traits and you have to take care of the results of their uneducated choices yourself.
If you know anyone who is inbred stay far, far away from them and their family. If not for the lack of morals, education and common sense; Then for your kids sake. Sometimes the genetic damage done by this practice skips a generation so if you have kids, they will be slobbering unproductive costly burdens on you till they die, or your kids will be raped by the inbred family members, cause that's how they roll.
If you dating anyone where the parents of the person are related by blood. IE: are the parents brother, sister's, Parent, child, any number cousins, uncles, nieces got together RUN!... Most inbreds all have a much higher incidences of mental retardation, deafness, crossed eyes, bad teeth, open cleft, and general deformities. Some even walk on all 4's, have hair on their faces, big ears like monkeys, and are generally unattractive. Entire families who practice even first cousin incest normally don't last more than a few generations. Or
Through DNA testing even the first child of incest will have markers, ie damage.
Examples: Misty Smith from St. Albans, Vermont
King Charles II of Spain and
The death of the Habsburg dynasty: uncle-niece and cousin unions of varying degrees.
Families in Utah inbred for generations: retardation after first incest offspring:http://www.deseretnews.com/article/635182923/Birth-defect-is-plaguing-children-in-FLDS-towns.html
http://en.wikipedia.org/wiki/Inbreeding