Why is it important to keep good relations with all the

Because family, this is the place where you can always return. The family is the most dear to you people and should be treated well. You need to be grateful to your parents for bringing you up to be such a decent, kind and well-bred person.

Your family will always stand by you in very decision you make, and will help you though hard times, they'll always be a part of you.  If your family relationship isn't strong you can feel alone and may not get the support you need.