Husband giving away money

My husband is currently in the military and I am not working because we both agreed it would pay off in the long term for me to finish school faster. His family does not have a lot of money, he pays for his fathers cell phone every month, he pays for his parents cable and internet bill, and whenever they're "tight" on money they come to him for it. His sister also hits him up for cash every once and a while and so does one of his brothers. My husband is the youngest of 4 children and he constantly has his family hounding him for cash.

I've tried talking to my husband about this and every time it ends in a massive fight. He thinks I'm making this a personal attack on his family. I told him when there is a serious situation and someone needs money, give it to them but when it's all the time, it is unnecessary. We are trying to save money right now and with me not working it's difficult enough but him giving away at least 500 dollars a month is ridiculous. How should I go about making him realize this is a serious situation? I am becoming extremely resentful towards his family and him and I feel like if this doesn't get straightened out soon, it can blow up into a bigger nastier problem then it is.