Your reaction is very human. It sounds, though, like you’re making judgements about them.
When i read shmiras halashon, a lesson a day, i found that i was less upset with the behaviors of others. Somehow, it helped me be dan lekaf zechus. Maybe that would help you, if your ultimate goal is to accept and move beyond this.
I think if you have no choice you can go in that direction. I’m not so sure you can’t work this through, though.
If you want to try to understand it, I would ask yourself these questions:
What’s your husband’s “take” on the situation (is he equally as upset? Why or why not?)
Why do you think they give to the other siblings and not you and your husband?
Have you ever asked them for money or help? Maybe the others do, which would explain why they have been helped and you have not.
It sounds like your effort to be self reliant is breeding resentment.
Do you think you might be expecting them to realize you’re struggling when they might be completely unaware?