It is unfortunate that your family isn't more supportive of your educational and career goals. Don't let their negativity and their lack of ambition get in the way of your dreams. Remember that some people, including myself, have accomplished a whole lot without any family support. Rely on your friends instead if your family fails you.
If you want to be a nurse, you should first try to get a taste of what it is really about by volunteering or working in the healthcare or human services field. You may find yourself becoming even more motivated to pursue a career as a nurse. Or you may find it distasteful or not at all what you expected.
Then you should start taking your pre-reqs. Many of your pre-reqs will have pre-reqs that you have to finish. For example, in order to take Anatomy and Physiology, you may have to take an introductory biolgoy classs, which may require a basic English class first. These courses are the foundation of any career in healthcare. Most nursing programs
these days wont even allow you to apply unless you have taken most if not all science pre-reqs.
As far as getting good grades are concerned, you can accomplish this in one of three ways. 1. You are already academically inclined and it is already very easy to get good grades. 2. The subject matter is so fascinating that you can't put down your books. (One great thing about nursing is that almost everything you learn, even in your pre-reqs, can be applied to your practice as a nurse). 3. You simply make the decision to do well and envision yourself studying at the same time each day and attending every class and adopting good study habits. Simple visualization is an extremely powerful tool.
Whatever you do, don't let a few defeated people in your family decide your life course for you. Just because they are washouts and haven't accomplished anything more than a minimum wage service industry job and a ten year old used car doesn't mean you have to settle too. If you have to do the LPN-RN-BSN route, go for it!