I think there are a number of issues here and several ways to address them, each with it's own relative merits.
My wife and I agree that family comes first but our view is that family means the two of us, first and foremost. Having sad that, we are both highly family oriented and are commited to and will continue to help our siblings, parents, etc.
Also, rather than sending money each month which causes dependency we (with the exception of school and associated fees) prefer to, like some suggested earlier in this thread, help them with cash-generating projcts.
I think that all money coming into a household money is for the household generally unless of course both parties agree to syphon off amounts for each individuals use. Others I imagine operate totally joint accounts and give as a couple. Each to their own. If you can't agree it's better to have separate accounts with agreed amounts put into it each month.
In theory it makes life easier when you pre-agree things prior to any marriage but we all know most such agreements can fly out of the window when a call comes through about some urgent and distant family need. Reaching some level of agreement is a good thing though. I also think that raising the subject with your wife and asking her for a possible solution given your financial circumstances might be a shrewed approach.
T