A "patent family" can be defined as all patent equivalents for a single invention. All of the published patent applications from various countries and the subsequent granted patents on an invention are commonly referred to as patent equivalents. They are not “true equivalents” in that each country may have different regulations for filing and different interpretations of the invention. It may include multiple patents in some countries because of differences in patent laws. When applying for a U.S. patent, inventors will need to know of any “prior art” which includes similar foreign patents or patent equivalents.
Many national patent offices now have individual web patent databases. Be aware that some sites are best searched in their native language.