Can you put your elder brother in dependent while Tax filing. He might need to sponsor his wife in the near future from Nepal. Does this tax filing might affect it to him later or make it better.

Thanks.

You can not put him as a dependent that will change your filing status ( single to head of household ) but you can put him for tax exempt ( $4000 ). There are some rules  need to be fulfilled. 

If he has to sponsor his wife better to file himself. Tax filing very important and immigration will ask for tax information.