This is generally known as "alternate" biochemistry; life based on compounds different from familiar terran life.
While such ethane or methane based life that could be found on the surface of Titan is indeed possible, it has several disadvantages to conventional carbon based life using water as a solvent.
While carbon life will probably predominate in the universe, it could be made up of wholly alien chemistry to our own. Reversed chirality of molecules, for example, could make alien life generally non-nutritional to us. Other molecules, mundane in their home ecosystem but alien to others, may have toxic, narcotic or even medicinal properties...