Have a long talk with your husband

Tell your hu*****and what your bottom line is and clear up with him about your family's financial situation.

He needs to set priority about your small family, his mom and his brothers. If you can't setup boundary about your financial situation now, your marriage will be in trouble eventually and you might put a lot of your own money to support his family if that's what you don't want to see.

Your hu*****and brought too much baggage to this marriage. It doesn't help if you keep complaining without actions.  

If your hu*****and's income can support your small family, his mom and brothers, I don't see big issue here. You just need to be a little generous financially and emotionally.