Saying "no"

As a few of you know, I have always had an issue saying no to my family- my mom and brother in particular.  I have lost a few thousand dollars being taken advantage of, stolen from, borrowed from... and then the only time I get a phone call is when they want me to do something else for them.  I am done with this nonsense.  Last year around this time, I lost $500 for a cell phone bill they ran up and didn't pay... then promised to pay back in time for summer tuition.  Here it is a year later, and that summer tuition went on a credit card.  My brother calls, wanting me to wire him money, and when I don't do it, he has my mom call me to ask me to do it.  He's lost his birth certificate 3-4 times in the past two years, and instead of putting it somewhere safe, it's now lost again.  He has no driver's license, and his state ID is cracked so he can't order one with his ID.  I suppose he better grow up and figure it out himself.  He texts to ask for money for various things, and I always say no.  He has never once called Becca, Lauren or Nick to just say hi or even Happy Birthday.  He makes me sick.