We have had this type of experience with family. DH and I do not make too much money but are comfortable. We own our own home, are putting our way through grad school/PhD, have one DD with a second on the way, have newer cars (took a lot of work to pay off

), and try to make 2 trips to WDW each year as our reward.
We have done our share of help for family members when it was needed. My parents were in a terrible financial bind and we offered that they move in with us to help with their finances, which has worked out well. We have also helped SIL whe her family needed the money. However I did have to inform DH that we would give them gift cards rather than cash so that it went to the desired item (ie: gas gift card, Safeway gift card, Mervyns gift card). Sometimes there are complaints as it's not "enough", they wanted the cash, or it wasn't to the "right" places. IMO just be greatful that someone is helping you out while realizing that they will probably NOT see the money again.
When we have borrowed money from family members we tell them they date that it will be returned and do our best to make sure that it is returned by that date. If there is a holdup (such as a weekend payday, which means wait until Monday not Friday) we let them know so they don't worry. However I do find it odd that the same people who borrow from us and rarely return it question whether WE will pay them back when we always do.
DH and I regualry receive critisizm from his family (and some of mine) regarding our family trips to Disney. They don't see the point to it and view it as a waste of money. They also then complain because we won't pay for them to go. Our response, is maybe if they didn't spend their $ on cigaretts, junk, or tatoos then maybe they'd have extra money. We have taken SIL 2 kids on various trip with us as thank you for babysitting or just becuase they would not go otherwise.
I do find it funny when DH stepmom complains that we are always taking DHs neice and nephew places but not his sepbrothers kids. Here is our answer, "they ahve a RICH uncle who could take then but instead decides not to. So next time ask him why he doesn't take them when he tells you about his next trip"
I will also add that we planned a huge family trip for next month to the world and just before payment was due SIL decided that since we weren't going to pay for her family to go that they didn't want to go with us. This caused a huge stink. But the 3 of us, plus my parents, and my brother and future SIL are all going as we each ahve apid our own ways.
So while i can't offer any advice I can offer my sympathy as I can relate. Just hang in there. You work for your money and are free to dow ith it as you choose (just like they do).