RELATIVE OR FAMILIAR?
So, imagine you are talking about your family or, more specifically, your wider family which includes your aunts and uncles, cousins and nephews and nieces. If you want to talk about your wider family in a generic way then it is best to use "a relative".
So, for example you might say: "I have a few relatives who live in Burgos". Spanish speakers will always be tempted to use "familiars" in this context but it is something you should avoid.
The only real use of "familiar" in English is when you have a certain amount of knowledge about something = "I am familiar with the concept of corporate responsibility"
Hope the helps!
Soy el director de Daniel Smith + Partners. Tengo más de 15 años de experiencia enseñando inglés a españoles.