Force to give support

I have a brother who is separated from his wife for 9 years. They have 1 daughter. My brother has new family with 3 children, and his ex wife has 2 other children with different father.  From the start, they got separated my brother gives support for his daughter in terms of milk, foods and other necessities.  Now, his ex wife demand for a higher support for their daughter, which my brother cannot give because he also has a family and children to support and his salary is not enough to give her demands. 

Is it right for his ex-wife to force my brother to oblige or to give a higher support, although he always gives the needs of their child for the school and for the monthly pay of the tutor? 

What are the cases his ex wife can charge him if he cannot give all the demands she wants? 

Hoping for your help and response.

according to the family code, the amount of support is based on the necessities of the child and the financial ability of the father. I suggest that your brother continue to support the child and let the ex wife resort to court to properly determine the amount of support. If your brother stop giving support, he can be held criminally and civilly liable.

Thank you for the response rollie002.