inlaws financially dependent help me pls

Dear All,

I have been a silent visitor to this site & posting my issues for the 1st time.Ours is a love marriage 3 yrs back.My parents were totally against it since my inlwas are uneducated,backward ppl & i belong to a modern middle class family.We are living in a nuclear family & my mil & fil,bil & sil are living in a village near to my place.During our affair, i had been to my inlwas place but i thought i wud never have to stay with them as my hubby rarely used to visit them.We both are working & managed to have furniture,utensils & other household items ouselves..My inlaws never bothered to see how we are living while they were happy with our marriage & i was fully accepted by them.
My hubby is very loving & caring only thing is that his brother does not earn well & hes married & his wife is expecting a kid in april & his father is a retrired man.in his marriage also we had to spend a handsome amount in my savings.My hubby wants to give full financial support to his brother & his baby also.I am not planning for another kid since i want to give everything best to my baby.Now,what my hubby is saying ,"VO BHI APNA HI BABY HOGA.AUR JO HUM HAMARAE BABY KE LIYE KARENGE,VAHI USKE LIYE KARENGE".He wants to help them in my sil's delivery also.The only thing which is making me crazy is i m leaving my 4 month old baby with a maid so that i can work & support my husband but he is not at all thinking about our future & my kids education.It has been happening if we go to mkt we always have to have double shopping,eg,if a purchase a bedsheet for our home,i have to purchase another one for my inlaws home since they are living in a village.Same thing is going to happen with my kid also.Whenever i will purchase anything for him ,ill have to purchase sumthing for my bil's kid also.I dont want to have an arguement with my hubby otherwise it will spoil the environment of my home.My inlaws are also very demanding,whenever we plan to visit them they give a huge list & we are giving them a fixed amount every month.
Please suggest me how to make my hubby more concerned for savings & our future without hurting him & to be very frank,i m working so that my baby can get everything he wants(otherwise im not very ambitious,i prefer to be at home & taking care of it),how can i bear my sil(devrani) sitting idle at home,enjoying her life & her baby is getting everything whatever my baby gets.Plese help me out with ur valuable suggestions im really very restless& insecure these days.