Jongdemdoomdoom

Hi, me and my sister are both over 18, and are dependent in a de facto(temporary) visa application for our mom and her partner. We stated that we are still studying as to why we are dependents even if we're over 18. We lodged the application last Dec 2016 and we're still waiting for the approval til now. We're currently in a tourist visa in australia. My first question is: how likely is it that our visa will get approved? We've been waiting for 6 months now, and we havent heard from them yet. this end month, our tourist visa will expire and i am planning on going back to our country but my sister and mom are planning on extending for another 3 months. My next question is: is me going back to our country alone and separated from my mom and sister will affect the decision of the embassy to our application? please help. Thank you!