The reason she had kids

I am the oldest of 4 kids, my parents are in a financial crisis because of poor financial spending and decisions. My brother who is 2 years younger than me has 4 kids and can't hold a steady job. His wife has been in college for 10 years and still has no degree, she actually stays enrolled to get the hardship money and spend it on other stuff. My sister just graduated H.S. parents bought her a new car, are paying for her apartment, and college at $40,000 a semester. Did I mention I am the only kid who has worked and not had a hand out from the parents. I have worked a 50 hour week or more since I was 14 years old and put myself through college, all while enduring abuse and neglect from my family because I chose not to be an athelete.
Well today my mom calls me and is hinting to borrow money or have me buy my sisters acne meds, because they can't afford them anymore.
She tells me she needs the help after she tells me that she just bought my sister a new laptop and my 35 year old brother a new PS3.
I told her I could not help because I will not enable them to live like they are and continue to enable the other kids not to work for anything.
She said the only reason I had you was to take care of us when we get old.After you were born, I wanted more because I figured the more kids I have, the better chance I have of being taken care of when I am old.
I can't believe she said that,I am sure it was out of anger because I will not help them.
I do not see it as my responsibilty to help them,when they make bad decisions with money and I am the only kid that has ever worked. I am also the only kid they never helped with anything and now all of a sudden since I am making very good money, I am supposed to take care of the whole damn family.
Sorry I just need to vent because I can't believe she could be so selfish.
And this woman can't figure out why I don't want any kids, I mean come on she made motherhood look so appealing and fun.