Relative and related are used in two different ways If someone is a relative they are in your family like a brother, sister, cousin, aunt, uncle If you are related to someone then you have a family connection to them, for example your brother is related to your sister, your aunt is related to your cousin. You can also use relative as an adjective in which you use it to compare other things or people of the same kind or when comparing the size or quality of two things, for example ' relative to the other school's exam results, Sam did well. or ' the relative strengths of the chemical mixtures. If something is related with something else it is connected or connercerned with it, for example , the rainfall statistics relate only to China' I am not an English teacher but a native english speaker so I hope this helps