It is called Astral projection , shamanic traveling or spiritual projection . It is not called Astro Projection .
Have you asked them to teach you how to astral project ? Since you have family members who can do that , that is a big bonus ! Just ask them for their guidance and tutelage . Ask them what books they read , what classes they attend and etc . So if you want to learn , just ask them .
If you want to work with the elements , then study it in depth and then practice it . Buy books and study then put it into practice .
To find out your elemental nature , it is the one that you feel most connected to . People have at least 2 elements they feel most connected to usually . Take note you can't choose it , like some say .