What should I do? Please help. Tips and advice would be great.?

Ultimately, you have to do what's best for you. Though your moms and sister's opinion matters to you, your the one that has to live your life and be responsible for all the choices made in it. If joining the military is what you want to do, then go for it. Your mom and sister might not be happy with the choice but if they love you, they will accept any choices that you make in your life. I wish you all the luck!